Linux Articles RSS Feed
How To Ping Specific Port Number
Viewed 158 times since Mon, Jun 1, 2020
Pinging ports is one of the most effective troubleshooting technique in order to see if a service is alive or not. Used by system administrators on a daily basis, the ping command, relying on the ICMP protocol, retrieves operational information about... Read More
Using grep to find string in files
Viewed 154 times since Fri, May 15, 2020
Using grep to find string in files How many times I had to search for something, let’s say my mac address, to change it in all files under /etc ? I couldn’t remebmer, different distros – different files, anyway, that’s an example, t... Read More
Linux RAID Mdadm Cheat Sheet
Viewed 119 times since Fri, May 15, 2020
Linux RAID Mdadm Cheat Sheet Mdadm is the modern tool most Linux distributions use these days to manage software RAID arrays; in the past raidtools was the tool we have used for this. This cheat sheet will show the most common usages of mdadm to mana... Read More
Securing /tmp and shm partitions
Viewed 107 times since Fri, May 15, 2020
Securing /tmp and /dev/shm is a nice practice.  Lots of programs and scripts have access in there. So you don’t want code, malicious or not to run in there, trying to get root permissions or snoop on you. Temporary storage directories such as /... Read More
20 IPtables Examples For New SysAdmins
Viewed 329 times since Fri, May 15, 2020
Linux comes with a host based firewall called Netfilter. According to the official project site: netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callb... Read More
Improve security with polyinstantiation
Viewed 97 times since Fri, May 15, 2020
If you’re concerned about protecting world-writeable shared directories such as /tmp or /var/tmp from abuse, a Linux® Pluggable Authentication Module (PAM) can help you. The pam_namespace module creates a separate namespace for users on your s... Read More
Install OpenVPN On CentOS / RHEL 7
Viewed 108 times since Fri, May 15, 2020
Security is most important aspect in internet. Outsiders can monitor internet traffic between your computer and the web. Here the importance of VPN comes. VPN, or virtual private network, is a secure method of connecting remote internet resources tog... Read More
Tip: SSD and Linux. Enable TRIM and check if it works
Viewed 101 times since Fri, May 15, 2020
What is TRIM? On hard disks, with spinning magnetic platters, you don’t care if a particular sector is being used by the operating system or not. If you want to use it again, just ask the controller to write into it, and the controller will jus... Read More
How to maximise SSD performance with Linux
Viewed 138 times since Fri, May 15, 2020
Now that SSDs have moved into the realm of affordability there’s little reason not to use one for your next PC if you’re not already using one. But Linux as with Windows has spent decades being tuned for spinning platter drives and while ... Read More
Learn how to align an SSD on Linux
Viewed 99 times since Fri, May 15, 2020
I’ve got a small home server with a software RAID-5 for storing my files. It also runs a few virtual machines and acts as a NAT router for internet access. Nothing expensive, just some Frankensteinian patchwork built from old hardware left over... Read More
Tips to Solve Linux & Unix Systems Hard Disk Problems
Viewed 100 times since Fri, May 15, 2020
Want to diagnose corrupt disk issues on a server? Want to find out why you are getting “disk full” messages on screen? Want to learn how to solve full/corrupt and failed disk issues. Try these eight tips to diagnose a Linux and Unix server hard disk ... Read More
Set Up SSH Tunneling on a Linux / Unix / BSD Server To Bypass NAT
Viewed 86 times since Fri, May 15, 2020
I’m a new Linux / Unix system user. How can I set encrypted tunnel between my desktop/laptop computer and server in a remote data center to bypass the limits in a network? How do I create a reverse SSH tunnel on Unix-like systems?SSH tunnelling... Read More
Top 20 OpenSSH Server Best Security Practices ssh linux aix
Viewed 77 times since Fri, May 15, 2020
OpenSSH is the implementation of the SSH protocol. OpenSSH is recommended for remote login, making backups, remote file transfer via scp or sftp, and much more. SSH is perfect to keep confidentiality and integrity for data exchanged between two netwo... Read More
How to Migrate from RHEL 8 to CentOS 8
Viewed 93 times since Fri, May 15, 2020
Live migration of a RedHat Enteprise Linux 8.0 to Centos 8.0 RHEL 8 to CentOS 8 migration guide. If you tried a RHEL 8 Beta or you have a Developer’s License of RedHat Enterprise Linux 8 and you want / need to migrate to CentOS 8 for any reason... Read More
Migrate a Linux System from Red Hat Enterprise to CentOS
Viewed 80 times since Fri, May 15, 2020
Migrate a Linux System from Red Hat Enterprise to CentOS Manually Migrating from RHEL to CentOS Here is how I started with a system with the Workstation edition of Red Hat Enterprise Linux 7 and converted that to CentOS. If you are planning in ... Read More
linux aix Killing a process and all of its descendants
Viewed 132 times since Tue, May 5, 2020
Killing a process and all of its descendants Written by @igor_sarcevic on August 2, 2019 Killing processes in a Unix-like system can be trickier than expected. Last week I was debugging an odd issue related to job stopping on Semaphore. More specif... Read More
linux ssh How to Hide the OpenSSH Version Details when Telnet to Port 22
Viewed 134 times since Wed, Apr 22, 2020
Information How to hide the OpenSSH version details when telnet to port 22 in Red Hat Enterprise Linux? Details OpenSSH version details are displayed from the file /usr/sbin/sshd. The only method to hide the version detail is to edit the binary fi... Read More
linux ssh Remotely Initiated Reverse SSH Tunnel
Viewed 122 times since Wed, Apr 22, 2020
Remotely Initiated Reverse SSH Tunnel This article lays out the steps to set up an SSH tunnel[1] so that you can connect to a server hidden behind a firewall/router. Cron is used on the server to maintain a connection from the hidden remote server... Read More
Linux ssh Hide OpenSSH Version Banner
Viewed 150 times since Wed, Apr 22, 2020
Hide OpenSSH Version Banner Here is a quick and dirty method for hiding some of the banner information advertised by OpenSSH[1]. This article focuses on how to use hexedit[2] to update your sshd binary to reduce information leakage. Hiding the ver... Read More
6 easy steps to setup offline two factor authentication in Linux
Viewed 215 times since Mon, Apr 6, 2020
6 easy steps to setup offline two factor authentication in Linux Table of Contents Lab Environment Google Authenticator with PAM Step 1: Install Google Authenticator on RHEL/CentOS 7 and 8 Linux Method 1: Install using DNF or YUM Method 2... Read More
CentOS / RHEL 7 : Configuring an NFS server and NFS client Linux NFS
Viewed 449 times since Fri, Feb 21, 2020
NFS allows a linux server to share directories with other UNIX clients over network. NFS server exports a directory and NFS client mounts this directory. RHEL 7 supports two version of NFS – NFSv3 and NFSv4. NFS server and RPC processes starting the ... Read More
Using renice and taskset to manage process priority and CPU affinity with Linux OEL 6.4
Viewed 318 times since Mon, Feb 17, 2020
Using renice and taskset to manage process priority and CPU affinity with Linux OEL 6.4 Table of Contents Overview Using renice and taskset to manage a Linux process Overview Process NICE priority values range from -20 to 19. ( see top NI... Read More
chrt command: Set / Manipulate Real Time Attributes of a Linux Process
Viewed 309 times since Mon, Feb 17, 2020
chrt command: Set / Manipulate Real Time Attributes of a Linux Process last updated March 6, 2008 in Categories Debian / Ubuntu, Linux, RedHat and Friends Q. How do I set the real time scheduling priority of a process under Linux operating system ... Read More
Fix rpmdb: Thread died in Berkeley DB library
Viewed 310 times since Fri, Feb 14, 2020
Fix rpmdb: Thread died in Berkeley DB library Aleksei Faians 3 months ago Updated Follow Synopsis: If you see rpmdb errors during package management (during yum/rpm operations), like this: rpmdb: Thread/process 277623/140429100390144 fail... Read More
Linux An introduction to swap space on Linux systems
Viewed 318 times since Thu, Jan 23, 2020
Learn how to modify the amount of swap space available on your Linux system, and how much you really need. 26 Sep 2018 David Both (Correspondent) Feed 179 up 5 comments Image by :  Opensource.com x Subscribe now ... Read More
Yum Update: DB_RUNRECOVERY Fatal error, run database recovery
Viewed 275 times since Fri, Jan 17, 2020
Yum Update: DB_RUNRECOVERY Fatal error, run database recovery Mattias Geniar, April 26, 2016 Follow me on Twitter as @mattiasgeniar If for some reason your server’s disk I/O fails during a yum or RPM manipulation, you can see the f... Read More
systemd Auto-restart a crashed service in systemd
Viewed 307 times since Fri, Jan 17, 2020
Mattias Geniar, January 13, 2020 Follow me on Twitter as @mattiasgeniar Systemd allows you to configure a service so that it automatically restarts in case it’s crashed. Take a typical unit file that looks like this. $ cat /etc/systemd/sy... Read More
Creating SWAP partition using FDISK & FALLOCATE commands
Viewed 265 times since Thu, Jan 16, 2020
Creating SWAP partition using FDISK & FALLOCATE commands by Shusain · Published April 18, 2019 · Updated April 18, 2019   Swap-partition holds the memory which is used in case the physical memory (RAM) is full . When RAM capacity has been uti... Read More
How to create stunnel with systemd? stunnel
Viewed 298 times since Thu, Jan 16, 2020
How to create stunnel with systemd? Solution Verified - Updated 2018-05-10T20:09:37+02:00 - English Environment Red Hat Enterprise Linux 7+ systemd stunnel Issue How to create stunnel with systemd? Resolution (Assuming Server side s... Read More
Linux Audit The Linux security blog about Auditing, Hardening, and Compliance lynis
Viewed 275 times since Thu, Jan 16, 2020
Lynis Screenshot of a security scan performed with Lynis. Security Auditing Lynis is our system and security auditing tool for Linux, Mac OS X, and UNIX-based systems. It provides insights in how well a system is hardened and what you can do, to i... Read More
Testing TLS/SSL encryption
Viewed 444 times since Thu, Jan 16, 2020
  testssl.sh is a free command line tool which checks a server's service on any port for the support of TLS/SSL ciphers, protocols as well as recent cryptographic flaws and more. NameLast ModifiedSizeType 2.6/ 2018-Nov-15 22:02:23 -- Dir... Read More
logrotate Log Rotate Configuration
Viewed 559 times since Sun, Jan 12, 2020
Some older versions of rsyslog may have trouble resuming on a log file after the log rotate has run. We can force rsyslog to pick up the new log file by adding a postrotate command in logrotate. This will restart rsyslog and delete the state files so... Read More
logrotate How log rotation works with logrotate
Viewed 751 times since Sun, Jan 12, 2020
Log rotation on Linux systems is more complicated than you might expect. Which log files are rotated, when and how often, whether or not the rotated log files are compressed, and how many instances of the log files are retained all depend on settings... Read More
logrotate Understanding logrotate utility
Viewed 254 times since Sun, Jan 12, 2020
Understanding logrotate utility Last updated on: 2019-12-20   Authored by: Jered Heeschen Logs are useful when you want to track usage or troubleshoot an application. As more information gets logged, however, log files use more disk space. Over tim... Read More
Logrotate Example for Custom Logs
Viewed 741 times since Sun, Jan 12, 2020
Logrotate Example for Custom Logs You will need this if you are using custom location for log files. Below is example for Nginx where log files are directly created in /var/www/example.com/logs You can put following in /etc/logrotate.d/nginx /var/... Read More
python learning
Viewed 363 times since Wed, Dec 18, 2019
https://automatetheboringstuff.com/   Python Tutorial: OS Module - Use Underlying Operating System Functionality: https://www.youtube.com/watch?v=tJxcKyFMTGo       https://www.cs.usfca.edu/~galles/visualization/Algorithms.html   https://runestone.aca... Read More
How to Configure ‘FirewallD’ in RHEL/CentOS 7 and Fedora 21
Viewed 574 times since Wed, Oct 9, 2019
Net-filter as we all know it’s a firewall in Linux. Firewalld is a dynamic daemon to manage firewall with support for networks zones. In earlier version, RHEL & CentOS 6 we have been using iptables as a daemon for packet filtering framework... Read More
Linux / UNIX: Run Command a Number of Times In a Row
Viewed 641 times since Tue, Aug 6, 2019
Linux / UNIX: Run Command a Number of Times In a Row last updated November 27, 2017 in Categories BASH Shell, Linux, UNIX   How do I run “foo” command 10 times (or n times) under Linux or UNIX like operating systems? You can use bash shell loop (... Read More
SSH ProxyCommand example: Going through one host to reach another server
Viewed 1296 times since Tue, Aug 6, 2019
SSH ProxyCommand example: Going through one host to reach another server last updated May 17, 2015 in Categories Linux, OpenBSD, UNIX   How do I use and jump through one server to reach another using ssh on a Linux or Unix-like systems? Is it poss... Read More
Applescript: Run or Call a Shell Script
Viewed 573 times since Tue, Aug 6, 2019
Applescript: Run or Call a Shell Script last updated January 15, 2017 in Categories Mac OS X, Programming, UNIX   How do run a shell script with an AppleScript? How do I integrate shell scripts into AppleScript? How do I call a shell script called... Read More
socat: Linux / UNIX TCP Port Forwarder
Viewed 838 times since Tue, Aug 6, 2019
socat: Linux / UNIX TCP Port Forwarder last updated March 15, 2010 in Categories Linux, Networking, UNIX How do I configure UNIX or Linux system to act as TCP port forwarder without using firewall? How do I install socat ( SOcket CAT ) multipurpos... Read More
How to run command or code in parallel in bash shell under Linux or Unix
Viewed 527 times since Tue, Aug 6, 2019
How to run command or code in parallel in bash shell under Linux or Unix last updated July 25, 2018 in Categories BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, RedHat and Friends, Suse, UNIX   How do I run commands in parallel in a bash she... Read More
How To Run Multiple SSH Command On Remote Machine And Exit Safely
Viewed 494 times since Tue, Aug 6, 2019
How To Run Multiple SSH Command On Remote Machine And Exit Safely last updated June 7, 2019 in Categories BASH Shell, CentOS, Debian / Ubuntu, FreeBSD, Linux, Networking, OpenBSD, RedHat and Friends, Suse, UNIX   I have a backup sync program on lo... Read More
RHEL7 slow ssh login
Viewed 756 times since Tue, Aug 6, 2019
RHEL7 slow ssh login Latest response February 5 2019 at 4:26 PM RHEL7: Symptom: 34 seconds to prompt password ssh login Solution (my case): - vi /etc/ssh/sshd_config - GSSAPIAuthentication no - service sshd restart Other Linux versión: vi /etc/ssh... Read More
How to recover error - Audit error: dispatch err (pipe full) event lost
Viewed 3709 times since Tue, Aug 6, 2019
How to recover error - Audit error: dispatch err (pipe full) event lost? Solution Unverified - Updated October 8 2018 at 10:28 AM - English Environment Red Hat Enterprise Linux 7.3 Issue Log file /var/log/messages showing audit error as... Read More
How to stop and disable auditd on RHEL 7
Viewed 4212 times since Tue, Aug 6, 2019
How to stop and disable auditd on RHEL 7? Solution Verified - Updated February 15 2018 at 9:19 PM - English Environment Red Hat Enterprise Linux 7 Issue Disclaimer: Links contained herein to external website(s) are provided for convenience... Read More
7 Tips – Tuning Command Line History in Bash
Viewed 1070 times since Fri, Jul 5, 2019
7 Tips – Tuning Command Line History in Bash Posted on Tuesday December 27th, 2016by admin   7 Tips that can help you to improve you Bash history file. You will learn how to add date and time to bash history file, increase history size, ignore spe... Read More
Use Fail2ban to Secure Your Server
Viewed 1477 times since Fri, Jul 5, 2019
What is Fail2BanPermalink Fail2ban is a log-parsing application that monitors system logs for symptoms of an automated attack on your Linode. When an attempted compromise is located, using the defined parameters, Fail2ban will add a new rule to iptab... Read More
18 Quick ‘lsof’ command examples for Linux Geeks
Viewed 679 times since Sun, Jun 30, 2019
lsof is a command line utility for all Unix and Linux like operating systems to check “list of open files” The name “lsof” is itself derived from this functionality. lsof command is mainly used to retrieve information about files that are opened by v... Read More
RHEL7: How to get started with Firewalld.
Viewed 1199 times since Wed, May 22, 2019
Note: This is an RHCSA 7 exam objective and an RHCE 7 exam objective. Presentation Firewalld is the new userland interface in RHEL 7. It replaces the iptables interface and connects to the netfilter kernel code. It mainly improves the security rules ... Read More
Super Grub2 Disk
Viewed 649 times since Wed, May 22, 2019
Super Grub2 Disk Super GRUB2 Disk helps you to boot into most any Operating System (OS) even if you cannot boot into it by normal means.   Super Grub2 Disk 2.01 rc2 Main Menu Tour Here there is a little video tour in order to discover most of Supe... Read More
10 nmap Commands Every Sysadmin Should Know
Viewed 570 times since Wed, May 22, 2019
10 nmap Commands Every Sysadmin Should Know Benjamin Cane Feb 25, 2013 8 min read Administration, Cheat Sheets, Linux, Linux Commands, Networking, Security, Unix, Unix Commands   Recently I was compiling a list of Linux commands that every... Read More
8 Vim Tips And Tricks That Will Make You A Pro User
Viewed 482 times since Fri, Apr 19, 2019
Brief: In this article, I’ll show you some of my favorites Vim tricks with practical examples. If you don’t use Vim, these tips might not give reasons for using Vim but if you use it already, you’ll definitely become a better Vim us... Read More
3 Ways to Check Linux Kernel Version in Command Line
Viewed 662 times since Fri, Apr 19, 2019
Brief: Wondering which Linux kernel version your system uses? Here are several ways to check kernel version in Linux terminal. You may find yourself in a situation when you need to know the exact Linux kernel version being used on your system. Thank... Read More
Easily Find Bugs In Shell Scripts With ShellCheck
Viewed 598 times since Thu, Apr 18, 2019
Brief: ShellCheck is a handy utility tool that warns you of possible syntax and simple logical errors, without executing. You can also use it with Atom text editor. As we all know, the terminal is an inseparable part of the Linux system. And behind e... Read More
Check Detailed CPU Information In Linux With CoreFreq [Advanced]
Viewed 569 times since Thu, Apr 18, 2019
Did you ever feel the need to check CPU info in Linux? Did you ever want to know the real speed of your CPU? Or which process is currently bound to a given core? Those seem to be the questions for experts only. But stay with me— like Alice, you... Read More
Tilix: Advanced Tiling Terminal Emulator for Power Users
Viewed 1233 times since Thu, Apr 18, 2019
Do you ever get bored of the default terminal emulator that comes with your Linux distro? If your distro uses GNOME shell or something similar, chances are you are using GNOME terminal or one of its variants. Well, that works alright most of the time... Read More
Easily Monitor CPU Utilization in Linux Terminal With Stress Terminal UI
Viewed 599 times since Thu, Apr 18, 2019
Brief: Monitoring CPU utilization in Linux becomes a bit better with Stress Terminal UI.  For we terminal lovers, the more terminal tools, the better.  I’ve covered a number of terminal tools before, including music player, file browser. Today,... Read More
Terminal based "The Matrix" like implementation
Viewed 451 times since Thu, Apr 18, 2019
CMatrix CMatrix is based on the screensaver from The Matrix website. It shows text flying in and out in a terminal like as seen in "The Matrix" movie. It can scroll lines all at the same rate or asynchronously and at a user-defined speed. CMatrix by ... Read More
Fake A Hollywood Hacker Screen in Linux Terminal linux FUN
Viewed 543 times since Thu, Apr 18, 2019
Brief: This tiny tool turns your Linux terminal into a Hollywood style real time hacking scene. I am in! You might have heard this dialogue in almost every Hollywood movie that shows a hacking scene. There will be a dark terminal with ascii text, di... Read More
20 Linux Command Tips and Tricks That Will Save You A Lot of Time linux
Viewed 1581 times since Thu, Apr 18, 2019
Brief: Here are some tiny but useful Linux commands, terminal tricks and shortcuts that will save you a lot of time while working with Linux command line. Have you ever encountered a moment when you see your colleague using some simple Linux commands... Read More
Monitoring bezpieczeństwa Linux: integracja auditd + OSSEC cz. I
Viewed 681 times since Fri, Apr 5, 2019
Artykuł poświęcony jest integracji dwóch znanych i sprawdzonych narzędzi opensource do monitoringu bezpieczeństwa: oprogramowania do audytu zmian w systemie Linux (auditd) i Host IDS OSSEC. Celem artykułu jest poznanie ograniczeń i wykorzystanie zale... Read More
Understanding System auditing with auditd
Viewed 1030 times since Fri, Apr 5, 2019
What is auditd Auditing system is an important part of system administration. It allows us to audit minute details related to what exactly is happening within the system. auditd is a userspace component to the Linux auditing system. This means that s... Read More
Learn Linux System Auditing with Auditd Tool on CentOS/RHEL
Viewed 489 times since Fri, Apr 5, 2019
System auditing simply refers to in-depth analysis of a specific targeted system: an audit is made up of an examination of the various parts which comprise that system, with critical assessment (and testing if required) in different areas of interes... Read More
How To Use the Linux Auditing System on CentOS 7
Viewed 640 times since Fri, Apr 5, 2019
Introduction The Linux Auditing System helps system administrators create an audit trail, a log for every action on the server. We can track security-relevant events, record the events in a log file, and detect misuse or unauthorized activities by in... Read More
What Is /dev/shm And Its Practical Usage
Viewed 580 times since Tue, Mar 12, 2019
What Is /dev/shm And Its Practical Usage last updated March 14, 2006 in Categories Linux /dev/shm is nothing but implementation of traditional shared memory concept. It is an efficient means of passing data between programs. One program will creat... Read More
Manage SSH Key File With Passphrase
Viewed 533 times since Tue, Mar 5, 2019
Manage SSH Key File With Passphrase Any serious DevOps will only ssh by key file. Not with password, right? And mostly our powerful key file can unlock many critical envs. Have you ever uploaded your private key to other envs, like jumpbox? Wha... Read More
Linux Proxy Server Settings – Set Proxy For Command Line
Viewed 479 times since Mon, Feb 18, 2019
To use a proxy on the Linux command-line, you can set the environment variables http_proxy, https_proxy or ftp_proxy, depending on the traffic type. These proxy server settings are used by the almost all Linux command-line utilities, e.g. ftp, wget, ... Read More
Open SSL Encrypt & Decrypt Files With Password Using OpenSSL
Viewed 696 times since Mon, Feb 18, 2019
OpenSSL is a powerful cryptography toolkit that can be used for encryption of files and messages. If you want to use the same password for both encryption of plaintext and decryption of ciphertext, then you have to use a method that is known as symme... Read More
Open SSL Creating Certificate Signing Request — CSR Generation
Viewed 556 times since Mon, Feb 18, 2019
A Certificate Authority will use a CSR to create your SSL certificate. What is a CSR? A CSR or ‘Certificate Signing Request’ is a block of encrypted text, that is generated on the server that the certificate will be used on. It contains i... Read More
Open SSL HowTo: Decode SSL Certificate
Viewed 476 times since Mon, Feb 18, 2019
Waht is an SSL Certificate? SSL Certificate provides security for your website by encrypting communications between the server and the person visiting the website. It contains information about your Organization and Certificate Authority. It also con... Read More
SSL HowTo: Decode CSR
Viewed 462 times since Mon, Feb 18, 2019
A Certificate Authority will use a CSR to create your SSL certificate. What is a CSR? A CSR or ‘Certificate Signing Request’ is a block of encrypted text, that is generated on the server that the certificate will be used on. It contains i... Read More
Moving SSL Certificate from IIS to Apache
Viewed 452 times since Mon, Feb 18, 2019
This procedure will help you to move or copy your SSL certificate, installed on an IIS server to an Apache server. Step 1: Export IIS certificate into a .PFX file Run mmc.exe Click the ‘Console’ menu and then click ‘Add/Remove Snap... Read More
OpenSSL: Find Out SSL Key Length – Linux Command Line
Viewed 426 times since Mon, Feb 18, 2019
From the following article you’ll learn how to find out a key length of an SSL Certificate from the Linux command line, using OpenSSL utility. The information about the key size can be retrieved from the several sources. We can get the informat... Read More
OpenSSL: Check SSL Certificate Expiration Date and More
Viewed 565 times since Mon, Feb 18, 2019
From this article you will learn how to connect to a website over HTTPS and check its SSL certificate expiration date from the Linux command-line. Besides of validity dates, i’ll show how to view who has issued an SSL certificate, whom is it is... Read More
HowTo: Create CSR using OpenSSL Without Prompt (Non-Interactive)
Viewed 735 times since Mon, Feb 18, 2019
In this article you’ll find how to generate CSR (Certificate Signing Request) using OpenSSL from the Linux command line, without being prompted for values which go in the certificate’s subject field. Below you’ll find two examples o... Read More
OpenSSL: Check If Private Key Matches SSL Certificate & CSR
Viewed 400 times since Mon, Feb 18, 2019
When you are dealing with lots of different SSL Certificates, it is quite easy to forget which certificate goes with which Private Key. Or, for example, which CSR has been generated using which Private Key. From the Linux command line, you can easily... Read More
How To: Create Self-Signed Certificate – OpenSSL
Viewed 444 times since Mon, Feb 18, 2019
What is a self-signed SSL certificate? A self-signed certificate is a certificate that is not signed by a trusted authority. Nevertheless, the self-signed certificate provides the same level of encryption as a $100500 certificate signed by a trusted ... Read More
HowTo: Send Email from an SMTP Server using the Command Line
Viewed 417 times since Mon, Feb 18, 2019
The SMTP (Simple Mail Transfer Protocol) is an Internet standard for electronic mail (Email) transmission across Internet Protocol (IP) networks. This tutorial shows how to connect to SMTP mail server and send an Email using the ‘telnet’ ... Read More
HowTo: Retrieve Email from a POP3 Server using the Command Line
Viewed 490 times since Mon, Feb 18, 2019
The POP3 (Post Office Protocol Version 3) is an application-layer Internet standard protocol used by local Email clients to retrieve Email from a remote server over a TCP/IP connection. This tutorial shows how to connect to POP3 mail server and manag... Read More
Check a Website Availability from the Linux Command Line
Viewed 434 times since Mon, Feb 18, 2019
You can easily test a a website availability from the Linux command line and get the status codes from the web-server using commands like TELNET or CURL. Check a website availability with CURL Execute the following command to check whether a web site... Read More
Telnet – Send GET/HEAD HTTP Request
Viewed 420 times since Mon, Feb 18, 2019
Telnet is a tool for connecting to servers on a given port for troubleshooting connection issues. One of the most common tasks that you can do via telnet – is connect to some web server and verify its health by checking the response code in HTTP head... Read More
SSH: Execute Remote Command or Script – Linux
Viewed 393 times since Mon, Feb 18, 2019
to ROCK? Start a GUI (graphical) application on a remote Linux workstation over SSH! Read more → Example Execute the local script.sh on the remote server: $ ssh root@192.168.1.1 'bash -s' < script.sh Read More
20 Practical Examples of RPM Commands in Linux rpm
Viewed 972 times since Mon, Feb 18, 2019
This article provides some useful 20 RPM command examples that might be helpful to you. With the help of these rpm command you can managed to install, update, remove packages in your Linux systems. Some Facts about RPM (RedHat Package Manager) RPM ... Read More
RHEL : How to deal with “CLOSE_WAIT” and “TIME_WAIT” connection
Viewed 3066 times since Thu, Feb 14, 2019
RHEL : How to deal with “CLOSE_WAIT” and “TIME_WAIT” connection by Ramdev · Published March 15, 2014 · Updated July 2, 2015   CLOSE_WAIT is the state for the TCP connection after the remote side has requested a shut down(FIN), and the TCP conn... Read More
HowTo: Kill TCP Connections in CLOSE_WAIT State
Viewed 768 times since Thu, Feb 14, 2019
HowTo: Kill TCP Connections in CLOSE_WAIT State Posted on Tuesday December 27th, 2016by admin   If you are seeing a large number of connections persisting in CLOSE_WAIT state, it’s probably a problem with the application itself. Restarting i... Read More
sed Delete / Remove ^M Carriage Return (Line Feed / CRLF) on Linux or Unix
Viewed 516 times since Thu, Feb 7, 2019
How can I remove the ^M or ^M (carriage Return / line feed ) from text file using sed under UNIX or Linux operating systems? A newline is nothing but end of line (EOL). It is a special character or sequence of characters signifying the end of a line... Read More
How to remove CTRL-M (^M) characters from a file in Linux
Viewed 407 times since Thu, Feb 7, 2019
Environment SUSE Linux Enterprise Server 11SUSE Linux Enterprise Server 12Novell GroupWise 2012Novell GroupWise 8Novell Data Synchronizer Mobility PackNovell GroupWise Mobility Service Situation How to remove CTRL-M (^M) blue carriage return characte... Read More
Extending Linux LVM partitions script
Viewed 461 times since Wed, Feb 6, 2019
Posted on December 8, 2014 by alpacapowered Here’s a script I wrote a while a go to extend LVM partitions on Linux machines. The script assumes that you have extended the existing underlying physical (or “virtual” if it’s a VM) storage... Read More
Script to Offline and Remove A Disk In Linux
Viewed 411 times since Mon, Jan 28, 2019
This script will offline and remove a hard drive from your Linux machine.  That doesn’t mean it physically pulls it out of your server Read More
HowTo: Find Out Hard Disk Specs / Details on Linux
Viewed 545 times since Mon, Jan 28, 2019
HowTo: Find Out Hard Disk Specs / Details on Linux last updated June 12, 2017 in Categories CentOS, Debian / Ubuntu, Hardware, Linux, RedHat and Friends, Suse, Troubleshooting   Can you tell me a Linux command to find out information about my hard... Read More
how to list all hard disks in linux from command line
Viewed 436 times since Mon, Jan 28, 2019
how to list all hard disks in linux from command line   Posted on June 24, 2015 by barkeep Hard Disk, Hard Drive, Disk Drive or Hard Disk Drive are all names for a data storage device (hardware device) for storing and retrieving digital informat... Read More
CentOS / RHEL : How to move a Volume Group from one system to another
Viewed 569 times since Mon, Jan 28, 2019
To move a whole volume group from one system to another, the vgexport and vgimport commands can be used. Below example involves the steps to move a volume group named “data_vg” from one system to another. The logical volume from this volume group is ... Read More
Linux LVM recovery
Viewed 1137 times since Wed, Jan 23, 2019
LVM recovery Few days ago i made mistake and forced fsck to check partition that contain LVM instead of logic volume, as result i got broken LVM metadata. I was unable to see volume group an logic volumes. pvs output looked like that: # pvs -v Scan... Read More
How to use yum-cron to automatically update RHEL/CentOS Linux 6.x / 7.x
Viewed 1167 times since Tue, Dec 4, 2018
The yum command line tool is used to install and update software packages under RHEL / CentOS Linux server. I know how to apply updates using yum update command line, but I would like to use cron to update packages where appropriate manually. How do ... Read More
Method 2 – Use shell scripts How to install yum cron on a CentOS/RHEL 6.x/7.x
Viewed 509 times since Tue, Dec 4, 2018
Method 2 – Use shell scripts Warning: The following method is outdated. Do not use it on RHEL/CentOS 6.x/7.x. I kept it below for historical reasons only when I used it on CentOS/RHEL version 4.x/5.x. Let us see how to configure CentOS/RHEL for yum a... Read More
LOGROTATE – ARCHIWIAZACJA LOGÓW
Viewed 474 times since Fri, Nov 30, 2018
Rosnące logi na dysku potrafią zniechęcić każdego administratora do logów. Pomocą tutaj okazuje się program Logrotate który pozwala w ładny sposób administrować logami.   Konfiguracja programu odbywa się na dwa sposoby. Opcje globalne oraz niezbędne ... Read More
INSTALACJA MIB SNMP W SYSTEMIE CENTOS/RHEL 6
Viewed 574 times since Fri, Nov 30, 2018
Zacznijmy od początku.Co to jest MIB? Jest to skrót od Management Information Base, a sam MIB jest prostą bazą w której są zapisane informacje o obiektach, a każdy obiekt to jakaś informacja.MIB są wykorzystywane przez SNMP, za pomocą którego można z... Read More
KONTO SFTP Z CHROOTEM Z UŻYCIEM OPENSSH-SERVER NA CENTOS/RHEL6
Viewed 401 times since Fri, Nov 30, 2018
Konta SFTP-only możemy chcieć użyć, gdy mamy zainstalowany na serwerze SSH (prawie zawsze) i udostępniamy dane  innemu systemowi, który loguje się i pobiera je (i ewentualnie usuwa), a nie chcemy instalować dodatkowej aplikacji jak FTPd czy HTTPd. Za... Read More
SPRAWDZONA KONFIGURACJA RSYSLOG I LOGROTATE, JAKO ZEWNĘTRZNEGO SERWERA SYSLOG
Viewed 1262 times since Fri, Nov 30, 2018
rsyslog jest domyślną aplikacją logującą w systemach RHEL6 /CentOS 6. Tak jak i inne syslogi, funkcjonuje w oparciu o pliki lokalne oraz zewnętrznie o domyślne porty TCP i/lub UDP 514. To, czy będziemy używać TCP, czy UDP, zależy od nas, odpowiada za... Read More
How log rotation works with logrotate
Viewed 1108 times since Fri, Nov 30, 2018
Log rotation on Linux systems is more complicated than you might expect. Which log files are rotated, when and how often, whether or not the rotated log files are compressed, and how many instances of the log files are retained all depend on settings... Read More
logrotate - rotates, compresses, and mails system logs.
Viewed 443 times since Fri, Nov 30, 2018
NAME logrotate - rotates, compresses, and mails system logs. SYNOPSIS logrotate [-dv] [--force] [-s|--state statefile] config_file .. DESCRIPTION logrotate is designed to ease administration of systems that generate large numbers of log files. It a... Read More
Understanding logrotate utility part 1
Viewed 460 times since Fri, Nov 30, 2018
Last updated on: 2016-06-29   Authored by: Jered Heeschen vi /etc/logrotate.d/file_name_of_service /var/log/log_file_name.log { rotate 8 daily dateext missingok notifempty compress size 20k create 0600 root root} missingok - do not output error if ... Read More
Sample logrotate configuration and troubleshooting part 2
Viewed 463 times since Fri, Nov 30, 2018
Last updated on: 2015-12-31   Authored by: Jered Heeschen Applying knowledge In the previous article we talked about what logrotate does and how you can configure it. In this article we’ll apply this new knowledge to putting together a log ro... Read More
HowTo: The Ultimate Logrotate Command Tutorial with 10 Examples
Viewed 827 times since Fri, Nov 30, 2018
Managing log files effectively is an essential task for Linux sysadmin. In this article, let us discuss how to perform following log file operations using UNIX logrotateutility. Rotate the log file when file size reaches a specific size Continue to ... Read More
Tcpdump Examples Linux
Viewed 2892 times since Fri, Nov 16, 2018
Tcpdump Examples Practical tcpdump examples to lift your network troubleshooting and security testing game. Commands and tips to not only use tcpdump but master ways to know your network. Knowing tcpdump is an essential skill that will come in ha... Read More
Increase A VMware Disk Size (VMDK) Formatted As Linux LVM without rebooting
Viewed 934 times since Wed, May 30, 2018
Increase A VMware Disk Size (VMDK) Formatted As Linux LVM without rebooting Mattias Geniar, Friday, August 27, 2010 - last modified: Sunday, July 24, 2016 To increase the size of your VMware Virtual Machine, you need to do 2 major steps. First, you ... Read More
Lsyncd: live file syncronization across multiple Linux servers
Viewed 1112 times since Wed, Oct 31, 2018
Lsyncd is a tool I discovered a few weeks ago. It is a synchronization server based primarily on Rsync. It is a server daemon that runs on the “master” server, and it can sync / mirror any file or directory changes within seconds into your “slaves” s... Read More
How to Install and use Lsyncd on CentOS 7 / RHEL 7 rsync
Viewed 978 times since Wed, Oct 31, 2018
Lsyncd stands for “Live Syncing Daemon“, as the name suggest lsyncd is used to sync or replicate files & directories locally and remotely after a specific time of interval. It uses rsync & ssh in the backend. Lsyncd works on Master and Slave ... Read More
How to Synchronize Directories Using Lsyncd in Linux
Viewed 1015 times since Wed, Oct 31, 2018
In this article, I'll explain how to install Lsyncd(Live Syncing Mirror Daemon) on Linux systems and how to synchronize remote and local directories in Linux.  Lsyncd is a light-weight live mirror solution that is comparatively easy to install w... Read More
12 Linux Rsync Options in Linux Explained
Viewed 660 times since Wed, Oct 31, 2018
In this article, I would show the different rync options to sync file/directories to the destination server. The main advantages of the rsync are: Speed: Initially copies the whole content between local and remote system. Next, it transfers only the ... Read More
10 Linux rsync Examples to Exclude Files/Directories
Viewed 475 times since Wed, Oct 31, 2018
Rsync (Remote Sync) is a most commonly used command for copying and synchronizing files and directories remotely as well as locally in Linux/Unix systems. With the help of rsync command you can copy and synchronize your data remotely and locally acro... Read More
Exclude multiple files and directories with rsync
Viewed 481 times since Wed, Oct 31, 2018
Exclude multiple files and directories with rsync Posted on September 9, 2013 Rsync is very powerful tool to take backups, or sync files and directories between two different locations (or servers). In a typical backup situation, you might want to... Read More
6 rsync Examples to Exclude Multiple Files and Directories using exclude-from
Viewed 494 times since Wed, Oct 31, 2018
Rsync is very powerful tool to take backups, or sync files and directories between two different locations (or servers). You know this already, as we presented you with practical examples on rsync earlier. In a typical backup situation, you might wan... Read More
How to Register and Enable Red Hat Subscription, Repositories and Updates for RHEL 7.0 Server
Viewed 1012 times since Mon, Oct 29, 2018
After the last tutorial on minimal installation of Red Hat Enterprise 7.0, it’s time to register your system to Red Hat Subscription Service and enable your system repositories and perform a full system update. Enable Red Hat Subscription, Rep... Read More
SYS: Configure a local repository. local repo
Viewed 613 times since Mon, Oct 29, 2018
SYS: Configure a local repository. Last updated on October 6, 2018 (11,511 views) - CertDepot — 29 Comments ↓ Share this link 0 0   Create a directory where packages will be stored: # mkdir /repo Two options: mount the distr... Read More
Using Official Redhat DVD as repository
Viewed 717 times since Mon, Oct 29, 2018
Creating a Redhat package repository admin Redhat 12 April 2016 Introduction If your Redhat server is not connected to the official RHN repositories, you will need to configure your own private repository which you can later use to inst... Read More
Need to set up yum repository for locally-mounted DVD on Red Hat Enterprise Linux 7
Viewed 760 times since Mon, Oct 29, 2018
Need to set up yum repository for locally-mounted DVD on Red Hat Enterprise Linux 7  SOLUTION VERIFIED - Updated February 27 2018 at 10:15 PM -  English  Environment Red Hat Enterprise Linux 7 Issue How to set up yum repository to use locally-... Read More
Enabling or disabling a repository using Red Hat Subscription Management
Viewed 857 times since Mon, Oct 29, 2018
Enabling or disabling a repository using Red Hat Subscription Management  SOLUTION VERIFIED - Updated October 9 2017 at 2:10 PM -  English  Environment Red Hat Enterprise Linux (RHEL) 5.7 or higher, 6.1 or higher Red Hat Subscription Management ... Read More
Find All Large Files On A Linux System
Viewed 619 times since Mon, Oct 29, 2018
The best way to find large files on your Linux system is to use the command line. This how-to will suggest a few methods for listing such files in specific directories or complete file systems.     Before getting started, we suggest you Learn Linux B... Read More
How To Find Largest Top 10 Files and Directories On Linux / UNIX / BSD find
Viewed 425 times since Mon, Oct 29, 2018
Use: find . -type f -size +4096c to find files bigger than 4096 bytes. And : find . -type f -size -4096c to find files smaller than 4096 bytes. Notice the + and - difference after the size switch. The -size switch explained: -size n[cwbkMG] Fi... Read More
Linux Find Large Files
Viewed 563 times since Mon, Oct 29, 2018
Linux Find Large Files last updated December 17, 2008 in CategoriesBASH Shell, CentOS, Debian / Ubuntu, Fedora Linux, File system, Linux, RedHat and Friends, Ubuntu Linux Q. How do I find out all large files in a directory?A. There is no single co... Read More
Automatic YUM Updates with Yum-cron
Viewed 458 times since Fri, Oct 26, 2018
This post will guide you how to use yum-cron to update system under CentOS/RHEL Linux. How do I configure yum automatic updates with yum-cron tool in Linux. How to set yum updates with yum-cron. What is Yum-cron?   The yum-cron is an optional packag... Read More
Install Security Patches or Updates Automatically on CentOS and RHEL
Viewed 396 times since Fri, Oct 26, 2018
One of the serious needs of a Linux system is to be kept up to date regularly with the latest security patches or updates available for the corresponding distribution. In a previous article, we’ve explained how to configure automatic security ... Read More
How to enable automatic security updates on CentOS 7 with yum-cron
Viewed 430 times since Fri, Oct 26, 2018
If CentOS helps to power your data center, you might be interested in knowing it is possible (and fairly easy) to enable the automatic updating of security updates. This is especially handy if you have a number of CentOS 7 machines and would like thi... Read More
YUM CRON Enabling automatic updates in Centos 7 and RHEL 7
Viewed 1269 times since Fri, Oct 26, 2018
In previous posts we’ve seen how to Enable automatic security update in Debian/Ubuntu and in Red hat enterprise or Centos 6, recently I’ve started to work with the new Red Hat Enterprise 7 and I’ve noticed that there are some intere... Read More
YUM CRON RHEL7: Configure automatic updates.
Viewed 397 times since Fri, Oct 26, 2018
Presentation The yum-cron package provides a convenient way to check for, download and apply updates automatically. Installation procedure Install the yum-cron package: # yum install -y yum-cron Start the yum-cron service: # systemctl start yum-cron ... Read More
CentOS / RHEL : Configure yum automatic updates with yum-cron service
Viewed 2084 times since Fri, Oct 26, 2018
yum-cron is an optional package starting from Red Hat Enterprise Linux 6, this is a plugin for yum. From man page of yum-cron : yum-cron is a simple way to call yum commands from cron. It provides configuration to keep repository metadata up to date,... Read More
Cron YUM How to use yum-cron to automatically update RHEL/CentOS Linux
Viewed 417 times since Fri, Oct 26, 2018
The yum command line tool is used to install and update software packages under RHEL / CentOS Linux server. I know how to apply updates using yum update command line, but I would like to use cron to update packages where appropriate manually. How do ... Read More
What is yum-cron ?
Viewed 1095 times since Fri, Oct 26, 2018
What is yum-cron ? Solution Verified - Updated March 8 2018 at 8:54 PM - English Environment Red Hat Enterprise Linux Server 6.x Red Hat Enterprise Linux Server 7.x Issue The yum-cron package provides a convenient way to check for, downl... Read More
20 Linux YUM (Yellowdog Updater, Modified) Commands for Package Management YUM
Viewed 2221 times since Thu, Oct 25, 2018
In this article, we will learn how to install, update, remove, find packages, manage packages and repositories on Linux systems using YUM (Yellowdog Updater Modified) tool developed by RedHat. The example commands shown in this article are practical... Read More
YUM How to use yum command on CentOS/RHEL
Viewed 2064 times since Thu, Oct 25, 2018
How do I use the yum command to update and patch my Red hat Enterprise Linux / CentOS Linux version 5.x/6.x/7.x server via RHN or the Internet? Can I use up2date command under a RHEL v5.x? up2date command was part of RHEL v4.x or older version. You ... Read More
15 Linux Yum Command Examples – Install, Uninstall, Update Packages
Viewed 858 times since Thu, Oct 25, 2018
15 Linux Yum Command Examples – Install, Uninstall, Update Packages by Balakrishnan Mariyappan on August 31, 2011 Tweet Installing, removing, and updating packages is a typical activity on Linux. Most of the Linux distributions provides ... Read More
RHEL7: Configure automatic updates.
Viewed 405 times since Wed, Oct 17, 2018
Presentation The yum-cron package provides a convenient way to check for, download and apply updates automatically. Installation procedure Install the yum-cron package: # yum install -y yum-cron Start the yum-cron service: # systemctl start yum-cron ... Read More
Enabling automatic updates in Centos 7 and RHEL 7
Viewed 532 times since Wed, Oct 17, 2018
In previous posts we’ve seen how to Enable automatic security update in Debian/Ubuntu and in Red hat enterprise or Centos 6, recently I’ve started to work with the new Red Hat Enterprise 7 and I’ve noticed that there are some intere... Read More
How to use yum-cron to automatically update RHEL/CentOS Linux
Viewed 362 times since Wed, Oct 17, 2018
The yum command line tool is used to install and update software packages under RHEL / CentOS Linux server. I know how to apply updates using yum update command line, but I would like to use cron to update packages where appropriate manually. How do ... Read More
How to use yum command on CentOS/RHEL
Viewed 1040 times since Wed, Oct 17, 2018
How do I use the yum command to update and patch my Red hat Enterprise Linux / CentOS Linux version 5.x/6.x/7.x server via RHN or the Internet? Can I use up2date command under a RHEL v5.x?up2date command was part of RHEL v4.x or older version. You ne... Read More
red hat 7 tmpfiles service
Viewed 419 times since Thu, Oct 11, 2018
/etc/tmpfiles.d/  create file zabbix.conf which includes D /run/zabbix 0777 root root systemctl status systemd-tmpfiles-setup.service systemctl | grep tmp tmp.mount loaded active mounted /tmp var-tmp.mount loaded active mounted /var/tmp systemd-tmpfi... Read More
How to mount software RAID1 member using mdadm
Viewed 443 times since Wed, Oct 3, 2018
Just a moment ago I connected my old hard drive and realized that it was a RAID member. $ sudo fdisk -l /dev/sdd Disk /dev/sdd: 250.1 GB, 250058268160 bytes 255 heads, 63 sectors/track, 30401 cylinders, total 488395055 sectors Units = sectors of 1 *... Read More
How to deal with dmesg timestamps
Viewed 533 times since Wed, Oct 3, 2018
By default dmesg command print kernel ring buffer using timestamp for each logged message. It is easy to change this behavior and display date/time in human readable form using just one additional parameter but sometimes it is not supported so I will... Read More
How to accurately determine when the system was booted
Viewed 469 times since Wed, Oct 3, 2018
It is very easy to tell how long the system has been running using uptime command, but the information when exactly it was booted is not so apparent, so I will show you two different ways to get it. The first way - the simplest one Use last command t... Read More
How to convert RAW image to VDI and otherwise
Viewed 1123 times since Wed, Oct 3, 2018
VirtualBox command-line interface (VBoxManage) provides an easy way to convert raw disk image to the VDI/VMDK format and otherwise. Let's assume that we have raw image of the sdb device: $ sudo dd if=/dev/sdb of=./sdb.raw To use it with Virtu... Read More
Linux PAM configuration that allows or deny login via the sshd server
Viewed 421 times since Wed, Oct 3, 2018
Linux PAM configuration that allows or deny login via the sshd server last updated July 30, 2006 in Categories Howto, Linux, Linux login control, Networking, OpenBSD, RedHat/Fedora Linux, Security, Suse Linux, Sys admin, UNIX The idea is very simp... Read More
Red Hat Enterprise Linux - Allow Root Login From a Specific IP Address Only
Viewed 379 times since Wed, Oct 3, 2018
Title: Red Hat Enterprise Linux - Allow Root Login From a Specific IP Address Only Object Name: mmr_kc-0119626 Document Type: Support Information Original owner: KCS - Linux Disclosure level: Public Version state: final Environment FACT:Red Hat Enter... Read More
Top 20 OpenSSH Server Best Security Practices - good article
Viewed 562 times since Mon, Oct 1, 2018
Top 20 OpenSSH Server Best Security Practices last updated May 16, 2018 in CategoriesCentOS, Debian Linux, fedora linux, FreeBSD, Gentoo Linux, Howto, Linux, Networking, package management, RedHat/Fedora Linux,Security, Suse Linux, Sys admin, Ubuntu... Read More
Turbocharge PuTTY with 12 Powerful Add-Ons – Software for Geeks #3
Viewed 869 times since Sun, Sep 30, 2018
This article is part of on-going Software For Geeks series. PuTTY is hands-down the best, free, and lightweight SSH client for Windows. I have provided list of 12 powerful PuTTY add-ons with screenshots, that will solve few shortcomings of the origin... Read More
Top 25 Best Linux Performance Monitoring and Debugging Tools
Viewed 1836 times since Sun, Sep 30, 2018
I’ve compiled 25 performance monitoring and debugging tools that will be helpful when you are working on Linux environment. This list is not comprehensive or authoritative by any means. However this list has enough tools for you to play around ... Read More
Linux / UNIX: DNS Lookup Command
Viewed 430 times since Sun, Sep 30, 2018
How do I perform dns lookup under Linux or UNIX or Apple OS X operating systems without using 3rd party web sites for troubleshooting DNS usage? You can use any one of the following dns lookup utility under Linux / UNIX. You can skip all 3rd party w... Read More
10 Linux DIG Command Examples for DNS Lookup
Viewed 394 times since Sun, Sep 30, 2018
Dig stands for domain information groper. Using dig command you can query DNS name servers for your DNS lookup related tasks. This article explains 10 examples on how to use dig command. 1. Simple dig Command Usage (Understand dig Output) When you pa... Read More
10 Linux nslookup Command Examples for DNS Lookup
Viewed 493 times since Sun, Sep 30, 2018
nslookup is a network administration tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or any other specific DNS record. It is also used to troubleshoot DNS related problems. This article provides few examples... Read More
List DNS records, nameservers of a domain from command line
Viewed 454 times since Sun, Sep 30, 2018
List DNS records, nameservers of a domain from command line Advertisement:Canagon.com - Website for $499, beautiful premade designs, high-performance hosting on all continents, dedicated support team. Learn more >   If you want to find out... Read More
Linux nslookup Command Examples for DNS Lookup
Viewed 505 times since Sat, Sep 29, 2018
nslookup is a network administration tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping or any other specific DNS record. It is also used to troubleshoot DNS related problems. This article provides few examples... Read More
Linux Cluster Tutorial
Viewed 450 times since Sat, Sep 29, 2018
https://www.alteeve.com/w/AN!Cluster_Tutorial_2#What.27s_New.3F Read More
linux manual tools
Viewed 527 times since Fri, Sep 28, 2018
Main Page   Active Directory with Winbind Advanced Vi Cheat Sheet Apache Tips Arch Installation Script Arch UEFI Installation Basic Vi Cheat Sheet CIFS Client Setup Compose Key Sequences Conversion Table DRBD Build Steps Debian GRC Client Debian Ins... Read More
Stunnel Setup
Viewed 3044 times since Fri, Sep 28, 2018
Stunnel Setup   Contents 1 Overview 1.1 Wiki Conventions 2 Installation 2.1 RHEL / CentOS 7 as Server 2.2 Ubuntu 14 as Client 3 Server Configuration 4 Client Configuration 5 Testing 6 References   Overview Stunnel is a SSL proxy designe... Read More
Tunnel SSH Connections Over SSL Using ‘Stunnel’ On Debian 7 / Ubuntu 13.10
Viewed 627 times since Fri, Sep 28, 2018
Tunnel SSH Connections Over SSL Using ‘Stunnel’ On Debian 7 / Ubuntu 13.10 By SK - December 30, 2013 6877   stunnel is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote serve... Read More
Setup SSL Tunnel Using Stunnel on Ubuntu
Viewed 425 times since Fri, Sep 28, 2018
The Stunnel program is designed to work as an SSL encryption wrapper between remote client and server. It can be used to add SSL functionality. What Stunnel basically does is that it turns any insecure TCP port into a secure encrypted port using Open... Read More
stunnel Howto A Guide to create SSL access to a HTTP-only webserver with stunnel
Viewed 453 times since Fri, Sep 28, 2018
1. Get the stunnel software Source is available at http://stunnel.mirt.net/, but many distributions already provide a precompiled package. In this example, I compiled it from scratch.   fm@susie:/home/devel> zcat ../software/stunnel-4.15.tar.gz ... Read More
HP-UX - Stunnel Configuration
Viewed 426 times since Fri, Sep 28, 2018
HP-UX - Stunnel Configuration Information Stunnel configuration procedure. Details The steps outlined below will generate a new private key and certificate request for a host, send the request to the local certificate authority on ${cahost}, then ... Read More
Installing and Configuring stunnel on CentOS 6
Viewed 873 times since Fri, Sep 28, 2018
Here's how to get stunnel up and running on a CentOS 6 server, and configure your local stunnel client to work with it. Server-side installation and configuration First, install stunnel itself on the server: [root@host ~]# yum -y install st... Read More
HOWTO: Use SSL/port 465 in smarthost stunnel
Viewed 513 times since Fri, Sep 28, 2018
Smarthost currently doesn’t permit to use port 465 with SSL to connect to a SMTP server: Tested in Nethserver V6.8 with Aruba SMTP server Maybe works in Nethserver V7 too 2017.06.21 EDIT: Yes, it works in v7 too This is the solution: Install s... Read More
Deskshare TLS over Stunnel
Viewed 437 times since Fri, Sep 28, 2018
Deskshare TLS over Stunnel Anchor link for: Deskshare_TLS_over_Stunnel_ Deskshare TLS over Stunnel Overview Architecture Client Changes Stunnel Installing Stunnel Configuring Stunnel Server Keys and Certs Starting Stunnel Adding the keystore to... Read More
Using stunnel and TinyProxy to obfuscate HTTP traffic
Viewed 1027 times since Fri, Sep 28, 2018
Recently there has been a lot of coverage in both tech and non-tech news outlets about internet privacy and how to prevent snooping both from service providers and governments. In this article I am going to show one method of anonymizing internet tr... Read More
How To Set Up an SSL Tunnel Using Stunnel on Ubuntu
Viewed 707 times since Fri, Sep 28, 2018
What’s Stunnel The Stunnel program is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote server. It can be used to add SSL functionality to commonly used inetd daemons like POP2, POP3, and ... Read More
Setting up encrypted tunnel using stunnel
Viewed 408 times since Fri, Sep 28, 2018
Setting up encrypted tunnel using stunnel To implement encrypted communication between Redis masters and slaves, we recommend using stunnel. Stunnel works as TLS encryption wrapper between client and server. This step-by-step tutorial will explain ho... Read More
stunnel bacula
Viewed 438 times since Fri, Sep 28, 2018
Using Stunnel to Encrypt Communications Prior to version 1.37, Bacula did not have built-in communications encryption. Please see the TLSCommEncryptionmainchapter of the Bacula Enterprise Main Manual if you are using Bacula 1.37 or greater. Without ... Read More
Using stunnel to Encrypt Database Connections
Viewed 993 times since Fri, Sep 28, 2018
Most RDBMS such as PostgreSQL and MySQL support TLS connections to encrypt the data on the wire between the application and the database. However there also seems to be applications here and there that don’t support TLS connections to the datab... Read More
stunnel basics and pki standards
Viewed 918 times since Fri, Sep 28, 2018
stunnel basics and pki standards   # REFERENCES [1] http://www.sslshopper.com/article-most-common-openssl-commands.html <---- a great collection of openssl commands [2] http://www.madboa.com/geek/openssl/ <---- a detailed "how-to" for most... Read More
stunnel: Authentication
Viewed 492 times since Fri, Sep 28, 2018
Either the TLS client, the TLS server, or both need to be authenticated: Server authentication prevents Man-In-The-Middle (MITM) attacks on the encryption protocol. Client authentication allows for restricting access for individual clients (access ... Read More
debian Debian/Ubuntu Linux: Find If Installed APT Package Includes a Fix/Patch Via CVE Number
Viewed 467 times since Sun, Sep 23, 2018
I am a Debian Linux server user. How do I view the changelog of an installed package and find out if given CVE includes a fix or patch? How do I see a fix or patch already applied to installed package on a Ubuntu or Debian LTS server? The changelog ... Read More
debian How to check Debian CVE status using python script
Viewed 466 times since Sun, Sep 23, 2018
Check current status of Debian Common Vulnerabilities and Exposures using simple python script and Security Bug Tracker. Python script I have used regular shell script at first, but it was too complicated after a while, as parsing HTML code using sed... Read More
debian How to Upgrade Debian 8 Jessie to Debian 9 Stretch
Viewed 624 times since Sun, Sep 23, 2018
How to Upgrade Debian 8 Jessie to Debian 9 Stretch Posted by Jarrod on June 17, 2017 Leave a comment (16) Go to comments   Debian 9 Stretch was released as the latest stable version of the Linux Debian operating system today. While you can install... Read More
debian Install a newer kernel in Debian 9 (stretch) stable
Viewed 465 times since Sun, Sep 23, 2018
When using the latest version of Debian 9 stable, even with all updates installed, by default, you can’t get a very recent kernel via the standard repositories in your package manager. While the idea of using Debian stable is to remain stable a... Read More
Linux Chage Command to Set Password Aging for User
Viewed 444 times since Tue, Sep 11, 2018
The command name ‘chage’ is an acronym for ‘change age’. This command is used to change the user's password's aging/expiry information. Any user can execute this command with the ‘-l’ option to view their... Read More
How to manage Linux password expiry with the chage command
Viewed 492 times since Tue, Sep 11, 2018
As a Linux admin, you're probably accustomed to passwd, chown, chmod, and chgrp...all commands for managing various elements of user accounts, files, and folders. There is another command that all Linux administrators must know: chage (think of ... Read More
Manage Linux Password Expiration and Aging Using chage
Viewed 1163 times since Tue, Sep 11, 2018
Best practice recommends that users keep changing the passwords at a regular interval. But typically developers and other users of Linux system won’t change the password unless they are forced to change their password. It’s the system adm... Read More
An easier way to manage disk decryption at boot with Red Hat Enterprise Linux 7.5 using NBDE
Viewed 1490 times since Mon, Aug 6, 2018
How many times have you had to staff the server room during the graveyard shift just to enter a password to unlock encrypted disks at boot time? Has this requirement kept you away from securing your data? What are your options? Red Hat has included d... Read More
RHEL7: Create and configure LUKS-encrypted partitions and logical volumes to prompt for password and mount a decrypted file system at boot.
Viewed 1049 times since Mon, Aug 6, 2018
Install the LUKS package (if it’s not already installed): # yum install -y cryptsetup Activate LUKS module: # modprobe dm_crypt Check the module is running: # lsmod | grep dm_crypt dm_crypt 12894 0 dm_mod 82839 9 dm_crypt,dm_mirror,dm_log Crea... Read More
linux unix aix banner /etc/issue
Viewed 510 times since Fri, Aug 3, 2018
### WARNING ### WARNING ### WARNING ### WARNING ### WARNING ### WARNING ###    This is a private computer system.  This computer system, including all    related equipment, networks, and network devices (specifically including    Internet access) is... Read More
OEL 7 – How to disable IPv6 on Oracle Linux 7
Viewed 3391 times since Fri, Aug 3, 2018
In case you are not interested in IPv6, you can use the following HowTo to disable it on Oracle Linux 7. Unless you have something very very special on your System, these 10 Steps should do it. First of all, check if IPv6 is active at all Add t... Read More
Linux Network (TCP) Performance Tuning with Sysctl
Viewed 2574 times since Fri, Aug 3, 2018
Linux Network (TCP) Performance Tuning with Sysctl   16Udostępnij   Submitted by Sarath Pillai on Sun, 11/10/2013 - 19:06 Before the Linux kernel version 1.3.57, there was no mechanism other than recompiling the ke... Read More
Linux Kernel /etc/sysctl.conf Security Hardening
Viewed 1754 times since Fri, Aug 3, 2018
How do I set advanced security options of the TCP/IP stack and virtual memory to improve security and performance of my system? How do I configure Linux kernel to prevent certain kinds of attacks using /etc/sysctl.conf? How do I set Linux kernel para... Read More
Kernel sysctl configuration file for Linux
Viewed 971 times since Fri, Aug 3, 2018
# Kernel sysctl configuration file for Linux # # Version 1.12 - 2015-09-30 # Michiel Klaver - IT Professional # http://klaver.it/linux/ for the latest version - http://klaver.it/bsd/ for a BSD variant # # This file should be saved as /etc/sysctl.conf... Read More
10 Linux cryptsetup Examples for LUKS Key Management (How to Add, Remove, Change, Reset LUKS encryption Key)
Viewed 851 times since Tue, Jul 31, 2018
LUKS is the disk encryption for Linux. First time when you encrypt a partition with LUKS (or when you select encrypt disk option during OS installation), you have to specify a password that will be used when you open the LUKS partition. But, after th... Read More
WatchDog watchdog.sh script for checking server running
Viewed 1766 times since Tue, Jul 31, 2018
#!/bin/bash # Service watchdog script # Put in crontab to automatially restart services (and optionally email you) if they die for some reason. # Note: You need to run this as root otherwise you won't be able to restart serv... Read More
watchdog How to restart a process out of crontab on a Linux/Unix
Viewed 1454 times since Tue, Jul 31, 2018
How to restart a process out of crontab on a Linux/Unix last updated December 25, 2017 in Categories CentOS, Debian / Ubuntu, FreeBSD, Linux, Suse, UNIX   I am a new Linux user and not familiar with crontab syntax. How do I use a cron job to resta... Read More
Watchdog script to keep an application running
Viewed 1235 times since Tue, Jul 31, 2018
I currently use an application called MxEasy on my linux servers to display video from a couple of IP cameras. The software is rather buggy and crashes occasionally. I've wrote a script that checks to see if the application is running and if its... Read More
Expand or grow a file system on a Linux VMWare VM without downtime
Viewed 519 times since Fri, Jul 27, 2018
When your VM’s file systems are running out of space and you want to provide more space to your VM and you can’t afford any downtime, there are basically two options. Either you delete some files on the file system or you expand your curr... Read More
Use inotify-tools on CentOS 7 or RHEL 7 to watch files and directories for events
Viewed 704 times since Fri, Jul 27, 2018
Today, I discovered that the package inotify-tools is nowhere to be found in standard CentOS7 or RHEL7 repositories. Alternatives like incron seem to be absent as well. The inotify-tools can be used to watch a directory or file for activity and take ... Read More
www.unixarena.com
Viewed 498 times since Fri, Jul 27, 2018
https://www.unixarena.com/ Read More
A Quick and Practical Reference for tcpdump
Viewed 1639 times since Fri, Jul 27, 2018
When it comes to tcpdump most admins fall into two categories; they either know tcpdump and all of its flags like the back of their hand, or they kind of know it but need to use a reference for anything outside of the basic usage. The reason for this... Read More
12 Tcpdump Commands – A Network Sniffer Tool
Viewed 542 times since Fri, Jul 27, 2018
12 Tcpdump Commands – A Network Sniffer Tool by Narad Shrestha | Published: August 20, 2012 | Last Updated: September 13, 2012     Download Your Free eBooks NOW - 10 Free Linux eBooks for Administrators | 4 Free Shell Scripting eBooks     In our pr... Read More
tcpdump usage examples
Viewed 444 times since Fri, Jul 27, 2018
Tcpdump usage examples October 1, 2014 In most cases you will need root permission to be able to capture packets on an interface. Using tcpdump (with root) to capture the packets and saving them to a file to analyze with Wireshark (using a regular... Read More
tcpdump
Viewed 562 times since Fri, Jul 27, 2018
Basic Examples Basic Communication Find Traffic by IP Filter by Source and/or Destination Show Traffic by Network Show Traffic by Port Show Traffic by Protocol Show IPv6 Traffic Find Traffic Using Port Ranges Find Traffic Based on Packet Size Wri... Read More
Using IOzone for Linux disk performance analysis
Viewed 2407 times since Wed, Jul 25, 2018
Who never had to measure the disk performances on a system? Speaking about Linux performance monitoring includes a significant part of disk performances. If you are facing applications or databases running slower than expected or than on other enviro... Read More
Linux: Disks diagnostic using smartctl
Viewed 682 times since Wed, Jul 25, 2018
Facing disk issues such as corruption or block defect is thankfully not happening frequently. However when it does, the diagnose may look sometimes like a real struggle. This is forgetting that disks integrate since years the S.M.A.R.T technology. Go... Read More
Linux: how to monitor the nofile limit
Viewed 596 times since Wed, Jul 25, 2018
In a previous post I explained how to measure the number of processes that are generated when a fork() or clone() call checks the nproc limit. There is another limit in /etc/limits.conf – or in /etc/limits.d – that is displayed by ‘ulimit -n&rs... Read More
FIO (Flexible I/O) – a benchmark tool for any operating system
Viewed 545 times since Wed, Jul 25, 2018
I have just attended an interesting session held by Martin Nash (@mpnsh) at UKOUG 14 – Liverpool: “The least an Oracle DBA Should Know about Linux Administration” . During this session I had the opportunity to discover some interesting commands ... Read More
Linux – How to check the exit status of several piped commands
Viewed 1151 times since Wed, Jul 25, 2018
As piping in bash commands is common and very usefull, controling the exit status of each piped commands in bash scripting can be vital, especially for backups. I was checking by a customer the backups of a critical MySQL instance and was surpris... Read More
How to do a Filesystem Resize (ext3/ext4) on Redhat running on VMware
Viewed 1181 times since Wed, Jul 25, 2018
A filesystem resize can be done in several ways, online, offline, with LVM2 or without LVM2.  However, this blog will describe how to do an online resize of ext3/ext4 filesystems where a virtual disk (vmdk) is online added to a VMware Redhat guest OS... Read More
List usernames instead of uids with the ps command for long usernames
Viewed 469 times since Wed, Jul 25, 2018
Have your ever faced such a situation. You have usernames in your /etc/passwd file with more than 8 characters. This is no problem for Linux at all, usernames may be up to 32 characters long, only your ps output might look a little scrambled. It show... Read More
Linux – Securing your important files with XFS extendend attributes
Viewed 477 times since Wed, Jul 25, 2018
Let’s say, the tnsnames.ora is a quite important file on your system, and you want to make sure that you notice when someone changes the file. Taking a look at the modification time of that file would be good idea, or not? Per default, the ls -... Read More
OEL 7 – How to disable IPv6 on Oracle Linux 7 – Follow Up
Viewed 632 times since Wed, Jul 25, 2018
This is a follow up to the Blog were I explained how to disable IPv6 on Oracle Linux 7. If you have done all the steps which I have explained here http://blog.dbi-services.com/oel-7-how-to-disable-ipv6-on-oracle-linux-7/  then you have already IPv6 s... Read More
Oracle Linux 7 – How to audit changes to a trusted file such as /etc/passwd or /etc/shadow
Viewed 1067 times since Wed, Jul 25, 2018
Linux auditing is quite powerful and a lot of different use cases might be handled via the auditing framework. However, in this blog I would like to show you, how to audit changes on trusted files, like /etc/passwd or /etc/shadow. Of course, you are ... Read More
How to enable Proxy Settings for Yum Command on RHEL / CentOS Servers
Viewed 732 times since Thu, Jul 19, 2018
How to enable Proxy Settings for Yum Command on RHEL / CentOS Servers How to enable Proxy Settings for Yum Command on RHEL / CentOS Servers by Pradeep Kumar · Published January 30, 2017 · Updated August 2, 2017   In most of the data center direct... Read More
What UUIDs can do for you
Viewed 471 times since Tue, Jul 17, 2018
What UUIDs can do for you Author: David Pendell If you've ever looked in your /etc/fstab file, you have may have seen an entry that looks like UUID=62fa5eac-3df4-448d-a576-916dd5b432f2 instead of a more familiar disk drive designation, su... Read More
How to retrieve and change partition’s UUID Universally Unique Identifier on linux
Viewed 479 times since Tue, Jul 17, 2018
How to retrieve and change partition's UUID Universally Unique Identifier on linux admin Uncategorised 28 March 2013 On some unix systems a hard drives partition is referred by to as Universally Unique Identifier( UUID ) instead ... Read More
Get UUID of Hard Disks [Update]
Viewed 509 times since Tue, Jul 17, 2018
Short Tip: Get UUID of Hard Disks [Update] There is an update to this post available: UUIDs and Linux: Everything you ever need to know. The Universally Unique Identifier can be used to identify a device independent form its mount point or device... Read More
UUIDs and Linux: Everything you ever need to know [Update]
Viewed 483 times since Tue, Jul 17, 2018
UUIDs and Linux: Everything you ever need to know [Update] What is so special about UUIDs in Linux? I don’t know! But here is everything you ever need to know about UUIDs on Linux. A single, simple short tip about looking up UUIDs in Linux f... Read More
VMWare tools free
Viewed 1638 times since Mon, Jul 16, 2018
http://vsphere-land.com/vinfo/free-tools Free Tools     Tool NameDescriptionCategoryDeveloperLink Veeam Backup Free Edition Veeam Backup Free Edition provides a number of powerful utilities for managing VMs. It complements your regular backup t... Read More
LUKS dm-crypt/Device encryption GUIDE
Viewed 566 times since Fri, Jul 13, 2018
LUKS dm-crypt/Device encryption GUIDE This section covers how to manually utilize dm-crypt from the command line to encrypt a system. Contents 1 Preparation 2 Cryptsetup usage 2.1 Cryptsetup passphrases and keys 3 Encryption options with dm-c... Read More
Index » Community Contributions » System encryption using LUKS and GPG encrypted keys for arch linux
Viewed 538 times since Fri, Jul 13, 2018
Intro Using arch linux mkinitcpio's encrypt hook, one can easily use encrypted root partitions with LUKS. It's also possible to use key files stored on an external drive, like an usb stick. However, if someone steals your usb stick, he can ... Read More
How to encrypt a partition with DM-Crypt LUKS on Linux
Viewed 522 times since Fri, Jul 13, 2018
How to encrypt a partition with DM-Crypt LUKS on Linux DM-Crypt is transparent drive encryption that is kernel module and part of the device mapper framework for mapping physical block device onto higher-level virtual block devices, it uses cryptogra... Read More
How to encrypt a partition using LUKS?
Viewed 508 times since Fri, Jul 13, 2018
How to encrypt a partition using LUKS?   Red Hat Enterprise linux provides you an interface to encrypt the partitions during the installation time, which is quite easy. In this tutorial we will be seeing how can we create a new partition and encrypt ... Read More
How To: Linux Hard Disk Encryption With LUKS [ cryptsetup Command ]
Viewed 711 times since Fri, Jul 13, 2018
How To: Linux Hard Disk Encryption With LUKS [ cryptsetup Command ]   Linux encryption methods There are two methods to encrypt your data: #1: Filesystem stacked level encryption eCryptfs – It is a cryptographic stacked Linux filesystem. eCryptfs st... Read More
LUKS List available methods of encryption for LUKS
Viewed 501 times since Fri, Jul 13, 2018
$ cryptsetup benchmark # Tests are approximate using memory only (no storage IO). PBKDF2-sha1 292752 iterations per second PBKDF2-sha256 221362 iterations per second PBKDF2-sha512 142010 iterations per second PBKDF2-ripemd160 277124 it... Read More
high swap space utilization in LINUX
Viewed 482 times since Fri, Jul 13, 2018
  high swap space utilization in LINUX This morning, I got a ticket that one LINUX machine is about to consume all its swap space….. I addressed this ticket very much like I would do it if this was AIX – only the commands to resolve this situati... Read More
SSH Essentials: Working with SSH Servers, Clients, and Keys
Viewed 1141 times since Wed, Jun 27, 2018
Introduction SSH is a secure protocol used as the primary means of connecting to Linux servers remotely. It provides a text-based interface by spawning a remote shell. After connecting, all commands you type in your local terminal are sent to the re... Read More
O’Reilly’s CD bookshelf
Viewed 4548 times since Wed, Jun 27, 2018
https://docstore.mik.ua/orelly/bookshelfs.html   The Java Reference Library, version 1.3 The Java Enterprise CD Bookshelf, Version 1.0 The Perl CD Bookshelf, version 1.0 ... Read More
Using Kerberos security with Server for NFS
Viewed 1034 times since Wed, Jun 27, 2018
Using Kerberos security with Server for NFS May 13, 2010 by JoseBarreto // 1 Comments Share 0 0 I’ll discuss how to configure a UNIX based NFS client to connect to Windows Server for NFS using Kerberos security with RPCSEC_GSS. Traditionally ... Read More
Epoch & Unix Timestamp Conversion Tools
Viewed 13747 times since Fri, Jun 22, 2018
The current Unix epoch time is  1529656113   Convert epoch to human readable date and vice versa  [batch convert timestamps to human dates] GMT: Friday, 22 June 2018 07:40:23Your time zone: piątek, 22 czerwca 2018 09:40:23 GMT+02:00 DST Yr Mon D... Read More
Do you Know These 5 Use of V$session View ?
Viewed 5165 times since Thu, Jun 21, 2018
Do you Know These 5 Use of V$session View ?     V$session view is the base of all information related to current system status like which user, How many session, Which query and how long query is waiting etc. V$session is the first place when DBA s... Read More
List of 10 Must Know Oracle Database Parameters for Database Administrator
Viewed 6042 times since Thu, Jun 21, 2018
List of 10 Must Know Oracle Database Parameters for Database Administrator     Database Parameters are environment variables for a database which can change database behavior according to value of the parameter. These are input values which are tak... Read More
What is OS Watcher Utility and How to use it for Database Troubleshooting ?
Viewed 2766 times since Thu, Jun 21, 2018
What is OS Watcher Utility and How to use it for Database Troubleshooting ?     Oracle OS Watcher (OSWatcher) is a tool to help Remote DBA's to trouble shoot Database performance, Cluster reboot, node eviction, DB server reboot, DB instance Cr... Read More
How to Analyze or Read OS Watcher Output in three easy steps -- With Example ?
Viewed 3064 times since Thu, Jun 21, 2018
How to Analyze or Read OS Watcher Output in three easy steps -- With Example ?     I assume, you have got Oracle OS Watcher (OSWatcher) logs and Database Administrator is facing slow database performance or System hang kind of situations. So, Next ... Read More
Top 4 Reasons for Node Reboot or Node Eviction in Real Application Cluster (RAC) Environment
Viewed 7445 times since Thu, Jun 21, 2018
Top 4 Reasons for Node Reboot or Node Eviction in Real Application Cluster (RAC) Environment Remote DBA usually face Node Reboots or Node Evictions in Real Application Cluster Environment. Node Reboot is performed by CRS to maintain consistency in Cl... Read More
A tcpdump Tutorial and Primer with Examples
Viewed 1394 times since Sun, Jun 17, 2018
  A tcpdump Tutorial and Primer with Examples Created: January 4, 2004 | Updated: October 30, 2017   Why tcpdump? Basics Examples Basic Communication Specific Interface Raw Output View Find Traffic by IP Seeing Packet Contents with Hex Output ... Read More
Procedura powiekszania OCFS2 online
Viewed 511 times since Fri, Jun 8, 2018
Procedurę wykonujemy po powiększeniu LUN na macierzy dyskowej   Zawsze wykonujemy backup file systemu, który powiększamy   Wykonujemy komendę df –kv lub  df –akP  (lepiej formatuje wynik POSIX) lub df -h -T | grep ocfs2 (tylko fs ocfs2)   df -h -... Read More
How to schedule crontab in Unix Operating Systems
Viewed 502 times since Fri, Jun 8, 2018
How to schedule crontab in Unix Operating Systems.   If you need to run some script at a specific time in a Unix box and wish to do so without manually executing it you could leverage on a program called cron. Through cron you can schedule a script t... Read More
Linux Health Check Commands
Viewed 492 times since Fri, Jun 8, 2018
Linux Health Check Commands   This document contains some of the commonly used linux commands when performing health check on a machine running Linux Operating System. To view overall performance. [root@myserver]# top Note: - By default is ... Read More
Linux - How to shutdown or reboot
Viewed 421 times since Fri, Jun 8, 2018
Linux - How to shutdown or reboot   To reboot. [root@myserver]# reboot or [root@myserver]# shutdown -r now or [root@myserver]# init 6 To shutdown the Operating System. By default shutdown command will bring the Operating System to runlevel 1... Read More
Linux - How to unlock and reset user’s account
Viewed 500 times since Fri, Jun 8, 2018
Linux - How to unlock and reset user's account   Sometimes a user cannot remote login to a linux machine might not due to just password expired issue. His/her account might have some other settings that prevent them from logging in. Below is a q... Read More
Linux - Cannot login from remote console but can access via ssh
Viewed 539 times since Fri, Jun 8, 2018
Linux - Cannot login from remote console but can access via ssh   If you are not able to access your Linux machine through it's remote console, you can give the below solution a try. Symptom : Not able to login to a Linux machine via remote co... Read More
Linux - How to get IP and MAC address of ethernet adapter in Linux
Viewed 480 times since Fri, Jun 8, 2018
Linux - How to get IP and MAC address of ethernet adapter in Linux   Question : How to get MAC address of ethernet adapter in Linux? Answer : ifconfig command can be used to obtain MAC address of ethernet adapter in Linux. Search for "HWaddr" value f... Read More
Linux - How to get network speed and statistic of ethernet adapter in Linux
Viewed 488 times since Fri, Jun 8, 2018
Linux - How to get network speed and statistic of ethernet adapter in Linux   Question : How to get network speed of ethernet adapter in Linux. Answer : "ethtool <ethX>" command can be used to get network speed of specific ethernet card in Linu... Read More
Linux - How to monitor CPU usage
Viewed 509 times since Fri, Jun 8, 2018
Linux - How to monitor CPU usage   In Linux, top can be used to monitor CPU usage of the system. Top is similar to topas in AIX though both are not the same. Question : How to monitor CPU usage in Linux? Answer : ps command can be used to report a s... Read More
Linux - How to monitor memory usage
Viewed 419 times since Fri, Jun 8, 2018
Linux - How to monitor memory usage   Question : How to monitor memory [%MEM] in Linux? Answer : ps command can be used to report a snapshot of the current processes in Linux. Use option aux and sort based on the column to get the top usage based on ... Read More
Linux - How to get CPU information
Viewed 470 times since Fri, Jun 8, 2018
Linux - How to get CPU information   Question : How to show information of CPU in Linux? Answer : Command dmidecode with option "t" followed by parameter "processor" could be used to show hardware information related to CPU in Linux. Example : [... Read More
Linux - How to get Memory information
Viewed 502 times since Fri, Jun 8, 2018
Linux - How to get Memory information   Question : How to show information of memory stick [DIMM] in Linux? Answer : Command dmidecode with option "t" followed by parameter "memory" could be used to show hardware information of memory stick [DIMM] in... Read More
How to automate SSH login with password? ssh autologin
Viewed 459 times since Fri, Jun 8, 2018
How to automate SSH login with password?   Before we begin, I would like to highlight that you are recommended to use public key authentication method if you want to setup login via ssh to any machines without the use of password instead of the metho... Read More
Linux - How to perform I/O performance test with dd command
Viewed 504 times since Fri, Jun 8, 2018
Linux - How to perform I/O performance test with dd command   Question : How to perform I/O performance test in Linux to find r/w speed? Answer :  It can be achieved using dd command. Example to test write speed : 1. Go to the directory location whe... Read More
Red Hat ADDING SWAP SPACE
Viewed 504 times since Fri, Jun 8, 2018
7.2. ADDING SWAP SPACE Sometimes it is necessary to add more swap space after installation. For example, you may upgrade the amount of RAM in your system from 128 MB to 256 MB, but there is only 256 MB of swap space. It might be advantageous to ... Read More
How To Add Swap Space on Ubuntu 16.04
Viewed 518 times since Fri, Jun 8, 2018
How To Add Swap Space on Ubuntu 16.04 PostedApril 25, 2016 396.9kviews LINUX BASICS UBUNTU UBUNTU 16.04 Justin Ellingwood Introduction One of the easiest way of increasing the responsiveness of your server and guarding against out-of-mem... Read More
Linux Add a Swap File – HowTo
Viewed 3553 times since Fri, Jun 8, 2018
Linux Add a Swap File – HowTo Posted onMay 18, 2006in CategoriesDebian / Ubuntu, File system, Linux, RedHat and Friends, Suse,Ubuntu Linux last updated May 3, 2017   Ineed additional swap space to improve my Linux server/desktop system performance... Read More
Create a Linux Swap File
Viewed 579 times since Fri, Jun 8, 2018
Create a Linux Swap File Last updated on: 2015-08-19   Authored by: Trey Hoehne Swap is space on a disk that is reserved to be used as virtual memory. When a Linux server runs out of memory, the kernel can move inactive processes into swap to make ... Read More
How To Create a Linux Swap File
Viewed 602 times since Fri, Jun 8, 2018
How To Create a Linux Swap File by Aaron Kili | Published: June 15, 2017 | Last Updated: June 15, 2017      Download Your Free eBooks NOW - 10 Free Linux eBooks for Administrators | 4 Free Shell Scripting eBooks     In this article, we will explain... Read More
Using etckeeper with git
Viewed 908 times since Sun, Jun 3, 2018
Using etckeeper with git on Ubuntu by Jeremy L. Gaddis on February 18, 2011 · 5 comments in System Administration       Though I think we would all agree that it’s important, the unfortunate fact is that myself and other members o... Read More
Red Hat Cluster Tutorial
Viewed 672 times since Sun, Jun 3, 2018
Contents 1 What's New? 1.1 A Note on Terminology 1.2 Why Should I Follow This (Lengthy) Tutorial? 1.3 High-Level Explanation of How HA Clustering Works 2 The Task Ahead 2.1 A Note on Patience 2.2 Technologies We Will Use 2.3 A Not... Read More
RHCS6: Debug and test multicast traffic between two hosts
Viewed 623 times since Sun, Jun 3, 2018
RHCS: Debug and test multicast traffic between two hosts # Tested on RHEL 5 & 6# Sometimes we may suspect of multicast traffic not working as expected. In this case we# may carry out following tests to figure out whether it is working or no... Read More
RHCS6: Reduce a Global Filesystem 2 (GFS2)
Viewed 567 times since Sun, Jun 3, 2018
RHCS: Reduce a Global Filesystem 2 (GFS2) # Unhappily, as indicated in gfs2_grow man page, "There is no way to shrink a GFS2 filesystem."# Destroy... and rebuild :) Read More
RHCS6: Mirror/unmirror a GFS2 volume
Viewed 638 times since Sun, Jun 3, 2018
RHCS: Mirror/unmirror a GFS2 volume # Tested on RHEL 6# Mirroring# ------------------------------------------------------------------------------------------# Given a simple gfs2 logical volume (note that type is 'linear' and all exte... Read More
RHCS6: Show/Add GFS2/GFS journals
Viewed 744 times since Sun, Jun 3, 2018
RHCS: Show/Add GFS2/GFS journals # Tested on RHEL 6/gfs2 and RHEL 5/gfs# GFS2 -------------------------------# Showing journals of a gfs2 filesystemgfs2_tool journals /<mountpoint>   journal2 - 128MB   journal3 - 128MB   journal1 - 128MB ... Read More
RHCS6: Extend an existing Logical Volume / GFS2 filesystem
Viewed 749 times since Sun, Jun 3, 2018
RHCS: Extend an existing Logical Volume / GFS2 filesystem # Tested on RHEL 6 # We are extending a given GFS2 filesystem like following one by adding 1GB:df -h /sharedfs   Filesystem            Size  Used Avail Use% Mounted on   /dev/mapper/gfsv... Read More
RHCS6: Create a new Logical Volume / Global Filesystem 2 (GFS2)
Viewed 675 times since Sun, Jun 3, 2018
RHCS: Create a new Logical Volume / Global Filesystem 2 (GFS2) # Tested on RHEL 6# I included this recipe as part of Red Hat Cluster Suite but, in fact, gfs2 is part of an# optional package and not part of Red Hat Cluster Suite.# In any case, ... Read More
RHCS6: Quorum disk and heuristics
Viewed 1200 times since Sun, Jun 3, 2018
RHCS: Quorum disk and heuristics # Tested on RHEL 6# A quorum disk is usually used as a tie-breaker to determine which node should be fenced# in case of problems.# It adds a number of votes to the cluster in a way that a "last-man-standing" sc... Read More
RHCS6: Clustered LVM
Viewed 728 times since Sun, Jun 3, 2018
RHCS: Clustered LVM # Tested on RHEL 6# Clustered LVM allows us to use a regular LVM volume group and logical volume on shared# storage, making all the objects accessible to all cluster nodes at the same time.# Clustered LVM uses 'clvmd�... Read More
RHCS6: Basic operations on clustered services
Viewed 689 times since Sun, Jun 3, 2018
RHCS: Basic operations on clustered services # Tested on RHEL 6# On a cluster like following one:root@mynodeA:/#> clustatCluster Status for mycluster @ Thu Sep 25 21:39:54 2014Member Status: Quorate Member Name                               ... Read More
RHCS6: Luci - the cluster management console
Viewed 788 times since Sun, Jun 3, 2018
RHCS: Luci - the cluster management console # Tested on RHEL 6# The Red Hat High Availability Add-On includes a web based management framework for# deploying, configuring and managing a high availability cluster known as Conga that# includes tw... Read More
RHCS6: Install a two-node basic cluster
Viewed 685 times since Sun, Jun 3, 2018
RHCS: Install a two-node basic cluster # Tested on RHEL 6 # Red Hat Cluster is quite complex as to explain every and all functionalities in a simple # recipe like this. There are many considerations that should be taken into account as # net... Read More
RHCS6: ’fencing’ basics
Viewed 682 times since Sun, Jun 3, 2018
RHCS: 'fencing' basics # Tested on RHEL 6# The act of 'fencing' is the process where one cluster node will be cut off from access to# shared storage by the other cluster nodes. This can be done either at the power level or#... Read More
RHCS: Configure an active/backup pacemaker cluster
Viewed 875 times since Sun, Jun 3, 2018
RHCS: Configure an active/backup pacemaker cluster # Tested on CentOS 7 # Note: For the commands here after, [ALL] indicates that command has to be run on the two #       nodes and [ONE] indicates that one needs to run it only on one of th... Read More
RHCS: Install a two-node basic cluster
Viewed 848 times since Sun, Jun 3, 2018
RHCS: Install a two-node basic cluster # Tested on CentOS 7   # Notes mainly from http://clusterlabs.org/pacemaker # Note: For the commands here after, [ALL] indicates that command has to be run on the two #       nodes and [ONE] indicat... Read More
ZPOOL: Remove an existing zpool
Viewed 585 times since Sun, Jun 3, 2018
ZPOOL: Remove an existing zpool # Tested on RHEL 6 & 7# WARNING: Pay special attention to any existing F.S. on the pool.# 'destroy' command will remove all pool's F.S. without asking for confirmationPOOLNAME=my_poolPOOLMNTP=`... Read More
ZPOOL: Verify/change properties of a zpool
Viewed 576 times since Sun, Jun 3, 2018
ZPOOL: Verify/change properties of a zpool # Tested on RHEL 6 & 7ZPOOL=my_pool# Check the properties of the zpoolzpool get all $ZPOOL   NAME     PROPERTY       VALUE       SOURCE   my_pool  size           19.9G       -   my_pool  capacity  ... Read More
ZPOOL: Detach a submirror from a mirrored zpool
Viewed 634 times since Sun, Jun 3, 2018
ZPOOL: Detach a submirror from a mirrored zpool # Tested on RHEL 6 & 7# Even if ZFS can use individual slices or partitions, it is recommended to use whole disks.# Having a mirrored zpool like following onePOOLNAME=my_poolzpool status $POOL... Read More
ZPOOL: Add a mirror to a concat zpool
Viewed 827 times since Sun, Jun 3, 2018
ZPOOL: Add a mirror to a concat zpool # Tested on RHEL 6 & 7# Even if ZFS can use individual slices or partitions, it is recommended to use whole disks.# Having a concat zpool like following onePOOLNAME=my_poolzpool status $POOLNAME     poo... Read More
ZPOOL: Grow a zpool by adding new device(s)
Viewed 612 times since Sun, Jun 3, 2018
ZPOOL: Grow a zpool by adding new device(s) # Tested on RHEL 6 & 7# Even if ZFS can use individual slices or partitions, it is recommended to use whole disks.# --------------------------------------------------------------------------------... Read More
ZPOOL: Create a new zpool for zfs filesystems
Viewed 750 times since Sun, Jun 3, 2018
ZPOOL: Create a new zpool for zfs filesystems # Tested on RHEL 6 & 7# ZFS is a combined file system and logical volume manager designed by Sun Microsystems.# The features of ZFS include protection against data corruption, support for high s... Read More
ZFS: Snapshots and clones on zfs filesystems
Viewed 718 times since Sun, Jun 3, 2018
ZFS: Snapshots and clones on zfs filesystems # Tested on RHEL 6 & 7 # A snapshot is an only-read photograph of a filesystem. When taking a snapshot, it is # stored in a way so further transactions on filesystem will only be carried out on... Read More
ZFS: Remove an existing zfs filesystem
Viewed 573 times since Sun, Jun 3, 2018
ZFS: Remove an existing zfs filesystem # Tested on RHEL 6 & 7# Choose the F.S. to removezfs list   NAME           USED  AVAIL  REFER  MOUNTPOINT   c_pool         349M  19.2G    30K  /c_pool   c_pool/zfs01   349M   675M   349M  /zfs01   c_po... Read More
ZFS: Verify/change properties of a zfs filesystem
Viewed 614 times since Sun, Jun 3, 2018
ZFS: Verify/change properties of a zfs filesystem # Tested on RHEL 6 & 7ZPOOL=c_poolZFSFS=zfs01# Check the properties of the filesystemzfs get all $ZPOOL/$ZFSFS   NAME          PROPERTY              VALUE                  SOURCE   c_pool/zf... Read More
ZFS: Grow/Shrink an existing zfs filesystem
Viewed 667 times since Sun, Jun 3, 2018
ZFS: Grow/Shrink an existing zfs filesystem # Tested on RHEL 6 & 7# Choose the F.S. to resize and verify current sizezfs list   NAME           USED  AVAIL  REFER  MOUNTPOINT   c_pool         204K  19.6G    30K  /c_pool   c_pool/zfs01    30K... Read More
ZFS: Create a new zfs filesystem
Viewed 625 times since Sun, Jun 3, 2018
ZFS: Create a new zfs filesystem # Tested on RHEL 6 & 7# Select the zpool where F.S. will be createdzpool list   NAME     SIZE  ALLOC   FREE    CAP  DEDUP  HEALTH  ALTROOT   c_pool  9.94G   120K  9.94G     0%  1.00x  ONLINE  -   m_pool  9.... Read More
linux-training.be gives you books for free to study Linux
Viewed 699 times since Sat, Jun 2, 2018
linux-training.be gives you books for free to study Linux. Just click on the links above for six html study guides, or below for pdf versions. Linux Fundamentals.pdf teaches you the very fundamentals of Linux (or Unix!). This book is for beginners,... Read More
LVM: Remove an existing Volume Group
Viewed 637 times since Sat, Jun 2, 2018
LVM: Remove an existing Volume Group # Tested on RHEL 5, 6 & 7VG=testvgvgdisplay -v $VG    Using volume group(s) on command line.  --- Volume group ---  VG Name               testvg  System ID  Format                lvm2  Metadata Areas  ... Read More
LVM: Reduce an existing Volume Group by removing one of its disks
Viewed 627 times since Sat, Jun 2, 2018
LVM: Reduce an existing Volume Group by removing one of its disks # Tested on RHEL 5, 6 & 7VG=testvg# Check disks owned by volume groupvgdisplay -v $VG | grep "PV Name"   PV Name               /dev/sde1   PV Name               /dev/sde2   P... Read More
LVM: Extend an existing Volume Group by adding a new disk
Viewed 603 times since Sat, Jun 2, 2018
LVM: Extend an existing Volume Group by adding a new disk # Tested on RHEL 5, 6 & 7# First, verify the disk/partition to use on the new VG with "fdisk" or any other similar# toolDISK=/dev/sdd1VG=vgdatabase# Initialize disk under LVMpvcreate... Read More
LVM: Create a new Volume Group
Viewed 631 times since Sat, Jun 2, 2018
LVM: Create a new Volume Group # Tested on RHEL 5, 6 & 7# First, verify the disk/partition to use on the new VG with "fdisk" or any other similar# toolDISK=/dev/sdbVG=newvg# Initialize the physical disk to be used by LVMpvcreate $DISK# Crea... Read More
LVM: Reduce SWAP size by removing a Logical Volume
Viewed 611 times since Sat, Jun 2, 2018
LVM: Reduce SWAP size by removing a Logical Volume # Tested on RHEL 5, 6 & 7# Check current swap volume(s) and its sizeroot@<server>:/#> cat /etc/fstab | grep swap/dev/rvg/swaplv         swap                    swap    defaults    ... Read More
LVM: Reduce SWAP size by shrinking existing Logical Volume
Viewed 733 times since Sat, Jun 2, 2018
LVM: Reduce SWAP size by shrinking existing Logical Volume # Tested on RHEL 5, 6 & 7# Check which is the swap volume and its sizeroot@<server>:/#> cat /etc/fstab | grep swap/dev/rvg/swaplv         swap                    swap    de... Read More
LVM: Extend SWAP size by growing existing Logical Volume
Viewed 655 times since Sat, Jun 2, 2018
LVM: Extend SWAP size by growing existing Logical Volume # Tested on RHEL 5, 6 & 7# Check which is the swap volume and its sizeroot@<server>:/#> cat /etc/fstab | grep swap/dev/rvg/swaplv         swap                    swap    defa... Read More
LVM: Extend SWAP size by adding a new Logical Volume
Viewed 640 times since Sat, Jun 2, 2018
LVM: Extend SWAP size by adding a new Logical Volume # Tested on RHEL 5, 6 & 7# Adding a file to swap space is not a common operation so we will focus on adding a LV# Check current swap volume(s) and its sizeroot@<server>:/#> cat /... Read More
LVM: Managing snapshots
Viewed 656 times since Sat, Jun 2, 2018
LVM: Managing snapshots # Tested on RHEL 6 & 7# LVM allows to take read/write snapshots of a logical volume. An snapshot consists of a# point-in-time copy of a logical volume that can be written to independently from the# original volume.# ... Read More
LVM: Rename root VG/LV
Viewed 962 times since Sat, Jun 2, 2018
LVM: Rename root VG/LV # Tested on RHEL 6 & 7# Carry out planned modifications: renaming the existing Volume Group and/or renaming# the Logical Volume(s). I just wanted to change the name of all LVs belonging to rootvg:lvs  LV   VG     Att... Read More
LVM: Reduce root PV/VG
Viewed 776 times since Sat, Jun 2, 2018
LVM: Reduce root PV/VG # Tested on RHEL 6 & 7# *** I recommend to backup all important data before carrying out an operation like the# one described here.# I carried out my RHEL installation without being careful about disk partitioning. No... Read More
LVM: Recovering Physical Volume Metadata
Viewed 648 times since Sat, Jun 2, 2018
LVM: Recovering Physical Volume Metadata # Tested on RHEL 5, 6 & 7# If the volume group metadata area of a physical volume is accidentally overwritten or# otherwise destroyed, you will get an error message indicating that the metadata area ... Read More
LVM: Move allocated PE between Physical Volumes
Viewed 738 times since Sat, Jun 2, 2018
LVM: Move allocated PE between Physical Volumes # Tested on RHEL 5.2# I need to free up and remove /dev/sdc disk from my system. As it makes part of "datavg"# Volume Group, and since it is not 100% free, I'll need to move the data from to ... Read More
LVM: Mount LVM Partition(s) in Rescue Mode
Viewed 858 times since Sat, Jun 2, 2018
LVM: Mount LVM Partition(s) in Rescue Mode # When system is not able to boot up due to OS problems we may be leaded to boot it into# Rescue Mode using a installation CD.# While booting in this mode, system will try to find out linux installatio... Read More
LVM: Remove a Filesystem / Logical Volume
Viewed 630 times since Sat, Jun 2, 2018
LVM: Remove a Filesystem / Logical Volume # Tested on RHEL 5, 6 & 7MNTPT=/testmntptVG=`mount | awk '{if ( $3 == "'$MNTPT'" ) print$1}' | cut -f4 -d'/' | cut -f1 -d '-'`LV=`mount | awk '{if ( $3 =... Read More
LVM: Reduce an existing Logical Volume / Filesystem
Viewed 618 times since Sat, Jun 2, 2018
LVM: Reduce an existing Logical Volume / Filesystem # Tested on RHEL 5, 6 & 7# *** It is not possible to reduce an xfs filesystem so this recipe is valid only for#     ext2/ext3/ext4 filesystems.# *** As of February 2016, new implementati... Read More
LVM: Extend an existing Logical Volume / Filesystem
Viewed 762 times since Sat, Jun 2, 2018
LVM: Extend an existing Logical Volume / Filesystem # Tested on RHEL 5, 6 & 7# Concatenated volume# ------------------------------------------------------------------------------------------MNTPT=/testmntptSIZE=500                  # Size t... Read More
LVM: Create a new Logical Volume / Filesystem
Viewed 678 times since Sat, Jun 2, 2018
LVM: Create a new Logical Volume / Filesystem # Tested on RHEL 5, 6 & 7# Concatenated volume# ------------------------------------------------------------------------------------------MNTPT=/testmntptOWNER=testusr.testgrpVG=testvgLV=testlvS... Read More
Inxi – A Powerful Feature-Rich Commandline System Information Tool for Linux
Viewed 8385 times since Sat, Jun 2, 2018
Inxi – A Powerful Feature-Rich Commandline System Information Tool for Linux by Aaron Kili | Published: February 20, 2017 | Last Updated: February 20, 2017     Download Your Free eBooks NOW - 10 Free Linux eBooks for Administrators | 4 Free Shell Scr... Read More
How to find your System details using inxi
Viewed 1075 times since Sat, Jun 2, 2018
There are so many free and paid applications available to display or find the Linux system details. Today, we will be discussing how to find your Linux desktop or server details using a simple and yet useful tool called “inxi”. It is free, open sourc... Read More
Inxi: Find System And Hardware Information On Linux
Viewed 802 times since Sat, Jun 2, 2018
Inxi: Find System And Hardware Information On Linux By SK - February 4, 2015 1131   We already have shown different applications and ways to find the system and hardware information on Linux. In that series, today we will see how to find such... Read More
PROCESSOR AND MEMORY INFORMATION
Viewed 734 times since Sat, Jun 2, 2018
PROCESSOR AND MEMORY INFORMATION grep processor /proc/cpuinfogrep model name /proc/cpuinfocat /proc/meminfofree Understanding BIOS keywords dmidecode --type {KEYWORD / Number }/usr/sbin/dmidecode --type 17 You need to pass dmidecode following ... Read More
IPTABLES linux
Viewed 9311 times since Sat, Jun 2, 2018
IPTABLES   Linux: 25 Iptables Netfilter Firewall Examples For New SysAdmins Posted on December 13, 2011in Categories Iptables, Linux, Linux distribution, Linux Embedded devices, Linux laptop last updated August 23, 2017   Linux comes with a host b... Read More
Linux Screen
Viewed 748 times since Sat, Jun 2, 2018
Linux Screen Linux Screen allows you to: Use multiple shell windows from a single SSH session. Keep a shell active even through network disruptions. Disconnect and re-connect to a shell sessions from multiple locations. Run a long running pro... Read More
CONFIGURE FOR ASM Linux
Viewed 732 times since Sat, Jun 2, 2018
CONFIGURE FOR ASM Step1: from racnode1 as ROOT user # fdisk /dev/sdaThe number of cylinders for this disk is set to 30401.There is nothing wrong with that, but this is larger than 1024,and could in certain setups cause problems with:1) software... Read More
LVM basic
Viewed 726 times since Sat, Jun 2, 2018
LVM SCAN a new disk ls -l /sys/class/scsi_host/grep mpt /sys/class/scsi_host/host?/proc_namefdisk -lecho "- - -" > /sys/class/scsi_host/host2/scan   OVERVIEW OF DISKS and PARTITIONS lsblk   Summary of Volume  Groups vgs (Volume G... Read More
Linux File Systems (mkfs, mount, fstab) ext4
Viewed 802 times since Sat, Jun 2, 2018
Linux File Systems (mkfs, mount, fstab) This article provides an introduction to Linux file systems, with specific reference to the information needed for the RHCSA EX200 and RHCE EX300 certification exams. Remember, the exams are hands-on, so it doe... Read More
CONFIGURE OCFS2
Viewed 1731 times since Sat, Jun 2, 2018
17. Install & Configure Oracle Cluster File System (OCFS2) Most of the installation and configuration procedures in this section should be performed on both Oracle RAC nodes in the cluster! Creating the OCFS2 filesystem, however, should only be e... Read More
A Simple Guide to Oracle Cluster File System (OCFS2) using iSCSI on Oracle Cloud Infrastructure
Viewed 1062 times since Sat, Jun 2, 2018
A Simple Guide to Oracle Cluster File System (OCFS2) using iSCSI on Oracle Cloud Infrastructure By: Gilson Melo | Senior Product Manager Oracle Cluster File System version 2 (OCFS2) is a general-purpose shared-disk file system intended for use in cl... Read More
Installing and Configuring an OCFS2 Clustered File System
Viewed 873 times since Sat, Jun 2, 2018
  Installing and Configuring an OCFS2 Clustered File System Apache CloudStack, cloud computing, KVM, open source Last year we had a project which required us to build out a KVM environment which used shared storage. Most often that would be NFS ... Read More
OCFS2 Cluster File System Setup Guide in Linux
Viewed 1386 times since Sat, Jun 2, 2018
OCFS2 Cluster File System Setup Guide in Linux   What is OCFS2? OCFS2 is a shared-disk cluster file system for Linux  Capable of providing both high performance and high availability.   Cluster-aware applications can make use of parallel I/O for hig... Read More
RHEL: XFS basic operations
Viewed 1201 times since Sat, Jun 2, 2018
RHEL: XFS basic operations # Tested on RHEL 6 & 7 # XFS filesystem supports up to 16 EiB filesystems and up to 8 EiB and directory structures # holding tens of millions entries. # On the other hand it is a single node filesystem. It comes... Read More
RHEL: How to change a USER/GROUP UID/GID and all owned files
Viewed 2273 times since Sat, Jun 2, 2018
RHEL: How to change a USER/GROUP UID/GID and all owned files # How to change a UID/GID and all belonging filesUSER=myuserOLDUID=7773NEWUID=7774GROUP=mygroupOLDGID=157NEWGID=158# Assign a new UID to USER. Any files which the user owns and which ... Read More
RHEL: udev rules basics
Viewed 1006 times since Sat, Jun 2, 2018
RHEL: udev rules basics # Tested on RHEL 6 & 7# 'udev' is a mechanism for maintaining device nodes on a server. It handles the management# of the devices nodes through the 'udevd' daemon as well as rules defined on the ... Read More
RHEL: What is "SysRq key" and how to use it
Viewed 1256 times since Sat, Jun 2, 2018
RHEL: What is "SysRq key" and how to use it # Tested on RHEL 5, 6 & 7# What is the "Magic" 'SysRq' key?# ------------------------------------------------------------------------------------------# According to the Linux kernel doc... Read More
RHEL: Display swap/RAM size
Viewed 849 times since Sat, Jun 2, 2018
RHEL: Display swap/RAM size # File containing information about system memory   /proc/meminfo# Display physical memory sizecat /proc/meminfo | grep MemTotal   MemTotal:     11508864 kB# Display swap sizecat /proc/meminfo | grep SwapTotal   Swap... Read More
RHEL: Forgotten ’root’ password / using single-user to gain access
Viewed 913 times since Sat, Jun 2, 2018
RHEL: Forgotten 'root' password / using single-user to gain access # Tested on RHEL 6 & 7# RHEL 6 -----------------------------------------------------------------------------------# Booting into single user mode is the easiest ... Read More
RHEL: Force system to prompt for password in Single User mode
Viewed 1356 times since Sat, Jun 2, 2018
RHEL: Force system to prompt for password in Single User mode # Tested on RHEL 5, 6 & 7# Due to security reasons, one may want to force system to prompt for root password even# in Single User mode# By default, system doesn't ask for pa... Read More
RHEL: Services basic management - systemd
Viewed 9246 times since Sat, Jun 2, 2018
RHEL: Services basic management - systemd # Tested on CentOS 7# systemd is the new Fedora init system adopted by Red Hat from RHEL 7 on.# It is backwards compatible with SysV init scripts, enhances the administrative process# and provides new ... Read More
RHEL: Services basic management - chkconfig
Viewed 2870 times since Sat, Jun 2, 2018
RHEL: Services basic management - chkconfig # Tested on RHEL 5 & 6 # If one of "on", "off", "reset", or "resetpriorities" is specified after the service name,# 'chkconfig' command changes the startup information for  the specified... Read More
RHEL: Retrieve and generate a unique SCSI identifier
Viewed 861 times since Sat, Jun 2, 2018
RHEL: Retrieve and generate a unique SCSI identifier # Tested on RHEL 5, 6 & 7# There are many situations were we may need a unique identifier for a SCSI device# (disk, etc.) to be identified in an unambiguous and persistent way.# To obtain... Read More
RHEL: How to rebuild and/or patch a RPM package
Viewed 948 times since Sat, Jun 2, 2018
RHEL: How to rebuild and/or patch a RPM package # Tested on RHEL 6 & 7 # If possible,  avoid creating packages as 'root' as this is quite dangerous because we # could delete or overwrite OS existing files. # Setup the folder str... Read More
Build a simple RPM that packages a single file
Viewed 969 times since Sat, Jun 2, 2018
Build a simple RPM that packages a single file # Tested on RHEL 6 & 7# The 'rpmbuild' command is used to build a binary RPM from source code, as configured# with a .spec file.# Install the necessary packages: rpm-build and rpmdevt... Read More
RHEL: Allowing users to ’su’ to "root" / Allowing ’root’ to login directly to the system using ’ssh’
Viewed 898 times since Sat, Jun 2, 2018
RHEL: Allowing users to 'su' to "root" / Allowing 'root' to login directly to the system using 'ssh' # Tested on RHEL 5, 6 & 7# Allowing users to "su" to 'root'# -------------------------------------... Read More
RHEL: Route network packets to go out via the same interface they came in
Viewed 1022 times since Sat, Jun 2, 2018
RHEL: Route network packets to go out via the same interface they came in # Tested on RHEL 6   # When working on a server with several network interfaces, if we don't define any specific # VLAN routing, all the outgoing traffic will usual... Read More
RHEL: Rename a network interface on RHEL 7
Viewed 1989 times since Sat, Jun 2, 2018
RHEL: Rename a network interface on RHEL 7 # Tested on CentOS 7 (Virtual server)# RHEL 6 introduced the Consistent Network Device Naming, feature that sets the name of# network interfaces in order to make locating and differentiating the interf... Read More
RHEL: Bonding network interfaces
Viewed 959 times since Sat, Jun 2, 2018
RHEL: Bonding network interfaces # Tested on RHEL 5, 6 & 7 # Red Hat Enterprise Linux allows administrators to bind multiple network interfaces# together into a single channel using the bonding kernel module and a special network# interfac... Read More
RHEL: Multipathing basics
Viewed 1130 times since Sat, Jun 2, 2018
RHEL: Multipathing basics # Tested on RHEL 5 & 6# DM-Multipath is a feature of Red Hat from RHEL 5 on and can be used to provide:## Redundancy: DM-Multipath can provide failover in an active/passive configuration. In an#   active/passive co... Read More
RHEL: Remove existing SAN LUNs
Viewed 918 times since Sat, Jun 2, 2018
RHEL: Remove existing SAN LUNs # Tested on RHEL 5 & 6 # Given following LUN, for instance: multipath -ll [...]    3600508b4000971cd0001000022fa0000 dm-0 HP,HSV210    [size=2.0G][features=0][hwhandler=0][rw]    \_ round-robin 0 [prio... Read More
RHEL: Rebuilding the initial ramdisk image
Viewed 1481 times since Sat, Jun 2, 2018
RHEL: Rebuilding the initial ramdisk image # Tested on RHEL 5, 6 & 7 # Sometimes it may be necessary to rebuild the initial ramdisk (also known as initrd or # initramfs) to include new kernel modules, files, etc. # RHEL 3, 4 & 5: Reb... Read More
RHEL: Displaying/setting kernel parameters - ’sysctl’
Viewed 969 times since Sat, Jun 2, 2018
RHEL: Displaying/setting kernel parameters - 'sysctl' # Tested on RHEL 6 & 7# Setting kernel parameters is a fairly straightforward task. If we check the file# /etc/sysctl.conf, we will see several attributes with their appropria... Read More
RHEL: Building a custom kernel on RHEL 6
Viewed 882 times since Sat, Jun 2, 2018
RHEL: Building a custom kernel on RHEL 6 # Tested on RHEL 6.4 i386# Notes mainly from http://wiki.centos.org/HowTos/Custom_Kernel# WARNING: Please note that customizing kernel is not supported by Red Hat Support Services# NOTE: It is advisable ... Read More
RHEL: Crash kernel dumps configuration and analysis on RHEL 7
Viewed 1071 times since Sat, Jun 2, 2018
RHEL: Crash kernel dumps configuration and analysis on RHEL 7 # The memory reserved for the kdump kernel is always reserved during system boot. That# means that the amount of memory is specified in the system's boot loader configuration.# ... Read More
RHEL: Crash kernel dumps configuration and analysis on RHEL 6
Viewed 1162 times since Sat, Jun 2, 2018
RHEL: Crash kernel dumps configuration and analysis on RHEL 6 Kernel dumps may provide invaluable insights when debugging serious issues.1.- Install following RPMs:         kexec-tools         crash    To be able to analyze crash dumps, followi... Read More
RHEL: Crash kernel dumps configuration and analysis on RHEL 5
Viewed 1157 times since Sat, Jun 2, 2018
RHEL: Crash kernel dumps configuration and analysis on RHEL 5 Apart from this recipe, more information about the configuration can be found inthe file “/usr/share/doc/kexec-tools-*/kexec-kdump-howto.txt“https://access.redhat.com/knowledge/docs/... Read More
RHEL: iSCSI target/initiator configuration on RHEL7
Viewed 1270 times since Sat, Jun 2, 2018
RHEL: iSCSI target/initiator configuration on RHEL7 # Tested on RHEL 7# iSCSI target configuration# ------------------------------------------------------------------------------------------# Install required package: targetcliyum install -y ta... Read More
RHEL: iSCSI target/initiator configuration on RHEL6
Viewed 987 times since Sat, Jun 2, 2018
RHEL: iSCSI target/initiator configuration on RHEL6 # Tested on RHEL 6# iSCSI target configuration# ------------------------------------------------------------------------------------------# Required package: scsi-target-utils# Some documentat... Read More
RHEL: Getting/Setting hardware clock’s time
Viewed 904 times since Sat, Jun 2, 2018
RHEL: Getting/Setting hardware clock's time # Tested on RHEL 6 & 7 # Just an extract from 'hwclock' man page   hwclock -r or hwclock --show   hwclock -w or hwclock --systohc   hwclock -s or hwclock --hctosys   hwclock --set -... Read More
Df command in Linux not updating actual diskspace, wrong data
Viewed 771 times since Wed, May 30, 2018
Df command in Linux not updating actual diskspace, wrong data Mattias Geniar, Friday, November 26, 2010 - last modified: Wednesday, March 29, 2017 This is an annoying problem on a lot of Linux distributions, and it can have several causes. Caused by... Read More
Split and Reassemble files
Viewed 883 times since Mon, May 28, 2018
I wrote this a few years back for LinuxQuestions.org. It was around 2004 from memory, and majority of the mail servers in Internet land only allowed for 2MB file attachments. This has now change, but I thought I’d post the article anyway. There... Read More
RHEL: Change system’s hostname
Viewed 982 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7 # RHEL 5 & 6 -------------------------------------------------------------------------------# Change hostname in /etc/sysconfig/network file# and run following command:hostname <new_hostname># Do not forget t... Read More
RHEL: Checking HBAs
Viewed 1386 times since Sun, May 27, 2018
# Tested on RHEL 6# Show the instances of FC ports connected to the pci bus:lspci | grep -i "Fibre"   07:00.0 Fibre Channel: QLogic Corp. ISP2532-based 8Gb Fibre Channel to PCI Express HBA (rev 02)   07:00.1 Fibre Channel: QLogic Corp. ISP2532-based ... Read More
RHEL: Adding a boot entry to GRUB/GRUB2 configuration
Viewed 1026 times since Sun, May 27, 2018
# Tested on RHEL 6 & 7# RHEL 6# ------------------------------------------------------------------------------------------# Adding a new entry to grub boot file is as simple as adding a new boot stanza, at the end# of the file, to /boot/grub/grub... Read More
RHEL: GPT/MBR partition tables (using disks larger than 2 TiB)
Viewed 956 times since Sun, May 27, 2018
# Tested on RHEL 6 & 7# Up to now the default type of the partition table of a hard disk is MBR (msdos). This# old method presents some problems like the limitation of having a maximum of four primary# partitions but the main problem is that we c... Read More
RHEL: Enabling standard ftp/telnet
Viewed 954 times since Sun, May 27, 2018
# Tested on RHEL 5# By default system is as secured as to be accesible only via ssh/sftp.# Enabling ftp# ------------------------------------------------------------------------------------------# 1.- Edit File /etc/xinetd.d/gssftp and change followi... Read More
RHEL: Manually encrypting a filesystem with LUKS
Viewed 942 times since Sun, May 27, 2018
# Tested on RHEL  7# LUKS, Linux Unified Key Setup-on-disk-format, allow encrypting partitions. By default, the# option to encrypt the file systems is unchecked during the installation, otherwise we will# be prompted for a passphrase every time the s... Read More
RHEL: Reserved space on a ext2/ext3/ext4 filesystem
Viewed 2289 times since Sun, May 27, 2018
# Tested on RHEL 6 & 7# By default, when creating a new ext2/ext3/ext4 filesystem, five percent of the partition# is reserved for the superuser, allowing root to carry out administrative tasks on the# filesystem in the eventuality that F.S. becom... Read More
RHEL: Extending the maximum inode count on a ext2/ext3/ext4 filesystem
Viewed 947 times since Sun, May 27, 2018
# Tested on RHEL 6 & 7 # An inode is a data structure that contains information about a file or directory. Inodes# rarely get used up when the file system has available space. Nevertheless, this may# happen when there is a large amount of small f... Read More
RHEL: Displaying system info (firmware, serial numbers... )
Viewed 1234 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7# Network interface cards driver, driver version, firmware version, and bus informationethtool -i eth0   driver: bnx2   version: 2.0.8-rh   firmware-version: bc 5.2.3 NCSI 2.0.6   bus-info: 0000:03:00.0cat /var/log/dmes... Read More
RHEL: Extending a vmdk (Virtual Machine disk)
Viewed 1013 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7 # This procedure may be carried out to make visible the new size of a disk that is already# presented and used by the OS and that has been extended at virtual server level.# Whenever possible I recommend to create a new... Read More
RHEL: Handling SCSI disks
Viewed 1010 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7 # Check devices currently known to the SCSI subsystem # ------------------------------------------------------------------------------------------ cat /proc/scsi/scsi    Attached devices:    Host: scsi0 Channel: 00... Read More
RHEL: Back-up/Replicate a partition table
Viewed 942 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7 # Given the importance of disk's partition table, one should consider to make a backup# in a regular basis in order to be able to restore it in case it will get corrupted,# modified or deleted by mistake.# We may st... Read More
RHEL: ACLs basics
Viewed 1364 times since Sun, May 27, 2018
Files and directories have permission sets for the owner of the file, the group associated with the file,and all other users for the system. However, these permission sets have limitations. For example, differentpermissions cannot be configured for d... Read More
RHEL: Reinstalling Boot Loader on the Master Boot Record (MBR)
Viewed 1046 times since Sun, May 27, 2018
# Tested on RHEL 5 & 6# In many cases, the GRUB boot loader can mistakenly be deleted, corrupted or replaced.# We can manually reinstall GRUB on the master boot record, using either "grub-install"# or the "grub" prompt.# Ensure the device.map fil... Read More
RHEL: Resize/disable /dev/shm filesystem
Viewed 1048 times since Sun, May 27, 2018
# Tested on RHEL 5, 6 & 7 # Notes from www.walkernews.net, www.generation-linux.fr and Red Hat web site# Thanks to big memory size, nowadays most of RAM is not used at all. It is thus possible# to allocate a part of this physical memory to be use... Read More
RHEL: Extending a multipath LUN
Viewed 1041 times since Sun, May 27, 2018
# Tested on RHEL 6# This procedure may be carried out to make visible the new size of a LUN that is already# presented and used by the OS and that has been extended at SAN storage level.# Whenever possible I recommend to create a new LUN at SAN level... Read More
RHEL: Scan and configure new SAN (fibre channel) LUNs
Viewed 1096 times since Sun, May 27, 2018
# Tested on RHEL 5 & 6 # Identify host adapters on the systemsystool -c fc_host   Class = "fc_host"     Class Device = "host3"       Device = "host3"     Class Device = "host4"       Device = "host4"ls /sys/class/fc_host   host3  host4# Rescan t... Read More
RHEL: Create a local RPM repository
Viewed 1035 times since Sun, May 27, 2018
# Tested on RHEL/CentOS 6 & 7# Mount the installation disk and copy packages from <cdrom>/Packages to a local directory.# I'll use /depot as local repository.# Once done, first of all, you have to install createrepo package:cd /depotll... Read More
Zabijanie wszystkich procesów użytkownika
Viewed 780 times since Thu, May 24, 2018
Z ałóżmy, że z jakiegoś typowego powodu (zabieranie zbyt dużej ilości zasobów systemowych lub przepustowości łącza) chcemy zabić wszystkie procesy użytkownika. Oczywiście znamy komendę: skill -9 -u użytkownik, ale załóżmy, że użytkownik ten ustawił w... Read More
Przekazywanie portów TCP rinetd
Viewed 1951 times since Thu, May 24, 2018
P rzedstawiony hack jest tłumaczeniem „Forwarding TCP Ports to Arbitrary Machines” z książki „Linux Servers Hacks” autorstwa Rob’a Flickenger’a udostępnionym on-line (Hack #48) na stronie http://hacks.oreilly.com. Do tłumaczenia zostało d... Read More
Tropienie pożeracza dysku
Viewed 811 times since Thu, May 24, 2018
P rzedstawiony hack jest tłumaczeniem „Playing Hunt the Disk Hog” z książki „Linux Servers Hacks” autorstwa Rob’a Flickenger’a udostępnionym on-line (Hack #15) na stronie http://hacks.oreilly.com. Do tłumaczenia zostało dodane także parę ... Read More
Używanie rsync poprzez Secure Shell
Viewed 823 times since Thu, May 24, 2018
P rzedstawiony hack jest tłumaczeniem „Using rsync over ssh” z książki „Linux Servers Hacks” autorstwa Rob’a Flickenger’a udostępnionym on-line (Hack #38) na stronie http://hacks.oreilly.com. Do tłumaczenia zostało dodane także parę infor... Read More
Logowanie za pomocą kluczy Secure Shell
Viewed 865 times since Thu, May 24, 2018
P rzedstawiony hack jest tłumaczeniem „Quick Logins with ssh Client keys” z książki „Linux Servers Hacks” autorstwa Rob’a Flickenger’a udostępnionym on-line (Hack #66) na stronie http://hacks.oreilly.com. Do tłumaczenia zostało dodane tak... Read More
Prosty skaner portów TCP w bash
Viewed 799 times since Thu, May 24, 2018
S kanery do portów są jak śrubokręty. Nigdy nie ma ani jednego w pobliżu kiedy jest najbardziej potrzebny. Z pomocą przychodzi powłoka bash: 1 2 3 4 5 6 7 8 9 10 11 12 #!/bin/bash for a in $(yes scan | head -1024)   do   (( start++ ))   if [... Read More
Netcat shell zabezpieczony hasłem
Viewed 782 times since Thu, May 24, 2018
Prosty skrypt autorstwa Vittorio Milazzo ukazujący sposób przyznania powłoki za pomocą netcat dopiero po podaniu hasła: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 #!/bin/bash ncpassword () { NC="/bin/netcat" PORT="999" PA... Read More
Szybkie sprawdzenie zewnętrznego adresu IP i hosta
Viewed 808 times since Thu, May 24, 2018
Szybkie sprawdzenie zewnętrznego adresu IP hosta za pomocą polecenia curl: 1 curl ifconfig.me/ip Reverse DNS: 1 curl ifconfig.me/host Read More
Nagrywanie sesji SSH do pliku
Viewed 924 times since Thu, May 24, 2018
Wszystkie polecenia oraz ich komunikaty wyjściowe zostaną zapisane do pliku srv_session.txt: 1 ssh login@server.com | tee -a srv_session.txt Read More
Jak wygenerować silne hasła jednorazowe w Linuksie?
Viewed 835 times since Thu, May 24, 2018
pwgen -sy 30 date +%s | sha256sum | base64 | head -c 30 ; echo strings /dev/urandom | grep -o '[[:alnum:]]' | head -n 30 | tr -d '\n'; echo < /dev/urandom tr -dc _A-Z-a-z-0-9 | head -c${1:-30}; echo; gpg --gen-random --armo... Read More
Odpalenie polecenia tylko na jedną godzinę
Viewed 800 times since Thu, May 24, 2018
Użycie polecenia timeout do uruchomienia wybranego polecenia na określony czas działania: timeout 1h tcpdump -n -i eth0 -w network.pcap not host 192.168.1.5 lub tcpdump -n -i eth0 -w & pid=$! ; (sleep 3600 ; kill $pid) Read More
OpenSSL – sprawdzanie czy klucz pasuje do certyfikatu
Viewed 822 times since Thu, May 24, 2018
Jak sprawdzić, czy klucz prywatny pasuje do wydanego certyfikatu? Powinny posiadać identyczny skrót SHA256: 1 openssl rsa -noout -modulus -in kluczdomeny.key 2> /dev/null | sha256sum - e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b9... Read More
Linux – delete the LUN and remove traces from OS
Viewed 837 times since Tue, May 22, 2018
In my previous article explained about how to delete disk from ASM library. In this article will learn to delete the LUN and remove traces from server. This article applicable for deleting ASM disk, standard partitioned disk and LVM physical volume. ... Read More
Linux get the list of FC HBA’s and WWPN
Viewed 912 times since Tue, May 22, 2018
This simple script gives you the list of FC HBA detected in system. It query the sysfs filesystem to get the available fibre channel HBA. Script works for most of the Linux flavors, as specially any of Redhat, SUSE, Fedora and Centos distributions. T... Read More
Top 10 darmowych i publicznych serwerów DNS
Viewed 819 times since Tue, May 22, 2018
1. Google: – 8.8.8.8, 8.8.4.4 2. OpenDNS: – 208.67.220.220, 208.67.222.222 3. Norton ConnectSafe: – 199.85.126.10, 199.85.127.10 4. Comodo Secure DNS: – 8.26.56.26, 8.20.247.20 5. DNS.Watch: – 84.200.69.80, 84.200.70.40 6. VeriSign Public DNS: – 64.4... Read More
How to sort IP addresses in Linux
Viewed 992 times since Sun, May 20, 2018
How to sort IP addresses in Linux Answer: When you have a file ip.txt contains a list of IP addresses, e.g. 127.0.0.2 127.0.0.1 10.10.10.1 To sort it, you can use the following command # sort -t. -k1,1n -k2,2n -k3,3n -k4,4n ip.txt 10.10.10.1 127.0.... Read More
How to find the largest files and directories in Linux?
Viewed 1000 times since Sun, May 20, 2018
How to find the largest files and directories in Linux? Answer: For example, to list out top 10 files and directories inside /opt, you can use the following command: # du -a /opt| sort -nr | head -n 10       source: http://www.linuxask.com/questio... Read More
BIND for the Small LAN
Viewed 1119 times since Sun, May 20, 2018
How to configure BIND 9 to act as a caching nameserver or as the nameserver for a local domain. Contents Why serve DNS locally? Building a caching nameserver BIND configuration: named.conf The root nameservers: named.root Defining localhost Defin... Read More
Jak ustawić LVM, jak robić snapshoty oraz automatycznie powiększać LV, czyli małe howto
Viewed 1297 times since Sun, May 20, 2018
1. Co to jest i do czego służy LVM (Logical Volume Manager) pozwala na grupowanie urządzeń w wirtualne Volume Group (VG, nie lubię polskich tłumaczeń ;p) z których potem można tworzyć Logical Volume (LV) czyli taki wirtualny odpowiednik partycji dysk... Read More
Extending Linux LVM partitions - scripts
Viewed 2043 times since Sun, May 20, 2018
Here’s a script I wrote a while a go to extend LVM partitions on Linux machines. The script assumes that you have extended the existing underlying physical (or “virtual” if it’s a VM) storage device prior to execution. It will rescan the ... Read More
How setting the TZ environment variable avoids thousands of system calls
Viewed 1093 times since Mon, May 21, 2018
In our previous blog post about Linux system calls, we explained the different system call methods and highlighted a very interesting method in particular: the vDSO system call method. The purpose of the vDSO system call method was to create a way fo... Read More
Fałszujemy rozpoznania skanerów #1
Viewed 978 times since Mon, May 21, 2018
Fałszujemy rozpoznania skanerów #1 Napisał: Patryk Krawaczyński 29/12/2015 w Bezpieczeństwo, Pen Test Brak komentarzy.  (artykuł nr 492, ilość słów: 356) I stnieje wiele poradników, instrukcji i tutoriali, jak korzystać z skanerów bezpieczeństwa, kt... Read More
Fałszujemy rozpoznania skanerów #2
Viewed 909 times since Mon, May 21, 2018
W pierwszej części pokazałem, jak łatwo za pomocą iptables sfałszować nasłuchujące usługi. W tym przykładzie zajmiemy się techniką zwaną banner grabbing. Proces ten powoduje, że skaner przechodzi do warstwy aplikacji i zaczyna zachowywać się, jak kli... Read More
Jak znaleźć najszybszy publiczny serwer DNS w Polsce?
Viewed 951 times since Mon, May 21, 2018
curl -s http://public-dns.info/nameserver/pl.csv > list; cat list | cut -d "," -f1 | \ xargs -i timeout 1 ping -c1 -w 1 {} | grep time | \ sed -u "s/.* from \([^:]*\).*time=\([^ ]*\).*/\2\t\1/g" | grep -v "1 pa... Read More
Configuring VLAN interfaces in Linux
Viewed 1199 times since Mon, May 21, 2018
In this post, we will see how to configure VLAN tagged interfaces on a Linux machine. This will allow you to connect your machine to different VLANs in your network using a single interface. In this example, am going to configure the VLAN tagging on ... Read More
How do I add ethtool settings to a network device permanently?
Viewed 1556 times since Mon, May 21, 2018
ethtool can be used to set options for many types of Ethernet devices. The /etc/sysconfig/network-scripts/ifcfg-ethX files can have the ethtool settings added to them so that the settings are saved and used every time the device is activated. For exa... Read More
“Too many authentication failures” with SSH
Viewed 1867 times since Mon, May 21, 2018
Whenever you try SSH to your server using pageant (with Putty) or ssh-agent, have you ever got similar error message as follows: "Received disconnect from 10.0.0.1: 2: Too many authentication failures for user-name" if YES is the answer, please cont... Read More