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Using stunnel to Encrypt Database Connections

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...

Secure Remote Logging to Central Log Server Using RSYSLOG on CentOS 6 / CentOS 7 and stunnel

Secure Remote Logging to Central Log Server Using RSYSLOG on CentOS 6 / CentOS 7 and stunnel Â Secure Remote Logging to Central Log Server via Encrypted stunnel Tunneling Here is how I set up a secure remote rsyslog server on my VPS that a...

ubuntu How to Reset Forgotten Root Password in Ubuntu

In this article, you will learn how to reset the forgotten root password onÂ Ubuntu 18.04 LTSÂ andÂ Ubuntu 20.04 LTS. Firstly, you need to eitherÂ power onÂ orÂ rebootÂ yourÂ UbuntuÂ system. You should get a grub menu as shown below. If you areÂ running your s...

Transform XML to CSV Format | Unix String Pattern Manipulation The Ugly Way

Transform XML to CSV Format | Unix String Pattern Manipulation The Ugly Way Updated:Â Jun 22, 2020 Â Â Disclaimer: I do not claim the below method to be the best optimum method of transforming XML to CSV format on the Unix command p...

Linux RedHat How To Create An RPM Package

1. Install Required RPM-Build Packages Â Â Â $yum install rpm-build rpmdevtools Â Â Â 2. Create the directory structure Â Â Â $rpmdev-setuptree Â Â Â The directory structure will look like this Â $ls -l rpmbuild/ total 24 drwxr-x--- 4 root ro...

30 Handy Bash Shell Aliases For Linux / Unix / MacOS

30 Handy Bash Shell Aliases For Linux / Unix / MacOS Author:Â Vivek GiteÂ Last updated:Â October 28, 2020Â 186Â comments AnÂ bash shell aliasÂ is nothing but the shortcut to commands. The alias command allows the user to launch any command or group of...

ubuntu How to Reset Forgotten Passwords in Ubuntu 16.04

Forgot your Ubuntu login password? Well, this quick tip is going to show you how to reset user (or root) password in Ubuntu 16.04 LTS. It’s easy to change a password in Ubuntu Linux viaÂ passwdÂ command. The key is how you can get into the root c...

ubuntu How to reset lost root password on Ubuntu 16.04 Xenial Xerus Linux

This guide will provide you with an information on how to reset lost root ( administrator ) password on Ubuntu 16.04. This guide assumes that you have the actual physical access to your Ubuntu 16.04 Linux box. Reboot to Grub Menu In the first step yo...

How To Use Systemctl to Manage Systemd Services and Units

Introduction systemdÂ is an init system and system manager that has widely become the new standard for Linux distributions. Due to its heavy adoption, familiarizing yourself withÂ systemdÂ is well worth the trouble, as it will make administering servers...

systemctl Use systemd to Start a Linux Service at Boot

What is systemd? systemd is a Linux system tool initially developed by the Red Hat Linux team. It includes many features, including a bootstrapping system used to start and manage system processes. It is currently the default initialization system on...

How to create a Systemd service in Linux

At times you create a script and then you want to have the scripts controlled by systemd or in some cases you wish to have the scripts getting restarted by itself when it is killed due to some reason. In such cases systemd in Linux helps to configure...

Linux How to reset a root password on Fedora

A system administrator can easily reset a password for a user that has forgotten their password. But what happens if the system administrator forgets the root password? This guide will show you how to reset a lost or forgotten root password. Note tha...

Fedora 32: Simple Local File-Sharing with Samba CIFS Linux

Sharing files with Fedora 32 using Samba is cross-platform, convenient, reliable, and performant. What is ‘Samba’? SambaÂ is a high-quality implementation ofÂ Server Message Block protocol (SMB). Originally developed by Microsoft for connec...

bash mistakes This page is a compilation of common mistakes made by bash users. Each example is flawed in some way.

Bash Pitfalls This page is a compilation of common mistakes made by bash users. Each example is flawed in some way. Â PomocSpisTreÅci for f in $(ls *.mp3) cp $file $target Filenames with leading dashes [ $foo = "bar" ] cd $(dirname "$f") [ "$foo" =...

Linux Customizing Bash

The outermost layer of your operating system â the part you interact with â is called theÂ shell. Fedora comes with several preinstalled shells. Shells can be either graphical or text-based. In documentation, you will often see the acronyms GUI (Graph...

How to configure an SSH proxy server with Squid

Sometimes you can’t connect to an SSH server from your current location. Other times, you may want to add an extra layer of security to your SSH connection. In these cases connecting to another SSH server via a proxy server is one way to get th...

Secure NTP with NTS

Many computers use the Network Time Protocol (NTP) to synchronize their system clocks over the internet. NTP is one of the few unsecured internet protocols still in common use. An attacker that can observe network traffic between a client and server ...

haproxy linux

Â Â HAProxy Documentation Converter Made to convert the HAProxy documentation into HTML. Â Â https://cbonte.github.io/haproxy-dconv/ Â HAProxy Documentation Converter Made to convert the HAProxy documentation into HTML.

stunnel Securing telnet connections with stunnel

Telnet is a client-server protocol that connects to a remote server through TCP over port 23. Telnet does not encrypt data and is considered insecure and passwords can be easily sniffed because data is sent in the clear. However there are still legac...

stunnel How To Encrypt Traffic to Redis with Stunnel on Ubuntu 16.04

How To Encrypt Traffic to Redis with Stunnel on Ubuntu 16.04 UbuntuSecurityRedisUbuntu 16.04 ByÂ Justin Ellingwood PostedNovember 8, 2016Â 5Â versionsÂ 49.7kviews Introduction Redis is an open-source key-value data store, using an in-memory ...

stunnel How To Set Up an SSL Tunnel Using Stunnel on Ubuntu

How To Set Up an SSL Tunnel Using Stunnel on Ubuntu UbuntuSecurityNetworking ByÂ Nima Karimi PostedOctober 21, 2013Â 2Â versionsÂ 321.5kviews Â Status:Â Deprecated This article is deprecated and no longer maintained. Reason Ubuntu 12.04 reach...

rabbitmq Troubleshooting TLS-enabled Connections

Troubleshooting TLS-enabled Connections Overview This guide covers a methodology and some tooling that can help diagnose TLS connectivity issues and errors (TLS alerts). It accompanies the main guide onÂ TLS in RabbitMQ. The strategy is to test the re...

How to Clear RAM Memory Cache, Buffer and Swap Space on Linux

How to Clear RAM Memory Cache, Buffer and Swap Space on Linux EditorJune 28, 2016Â CategoriesLinux CommandsÂ 94 Comments Â Like any other operating system, GNU/Linux has implemented a memory management efficiently and even more than that. But if an...

How to clear swap memory in Linux

How to clear swap memory in Linux Got swappiness? Learn how to set appropriate swap settings in Linux, and clear your swap's contents. Posted:Â February 25, 2020Â |Â byTyler CarriganÂ (Red Hat) Image Photo byÂ Kaboompics .com...

Managing temporary files with systemd-tmpfiles on Red Hat Enterprise Linux 7

Managing temporary files with systemd-tmpfiles on Red Hat Enterprise Linux 7 ByÂ Alessandro ArrichielloÂ September 20, 2016 Have you ever used a temporary directory? I’m guessing if you use a computer, you’ve used one of these. It&r...

zabbix linux How to solve apache error No space left on device: Cannot create SSLMutex

Diagnosis When Apache does not start and shows the following result while prompting it to start, check the error_log file, Starting httpd : [Failed] The following error in error_log file may be causing the issue ( /var/log/httpd/error_log ) [error] ...

Red Hat 8 How to Set Up Automatic Updates for CentOS 8

The best thing you can do for your data and machine is to keep them secure. It can be as easy as turning on updates. However, most people usingÂ CentOS 8Â don’t know how to do that. In this article, you are going to learn how to enable automatic ...

Linux 16 Useful Bandwidth Monitoring Tools to Analyze Network Usage in Linux

16 Useful Bandwidth Monitoring Tools to Analyze Network Usage in Linux Aaron KiliFebruary 13, 2020Â CategoriesMonitoring ToolsÂ 14 Comments Â Are you having problems monitoring your Linux network bandwidth usage? Do you need help? It’s import...

Linux 20 Netstat Commands for Linux Network Management

20 Netstat Commands for Linux Network Management Ravi SaiveJuly 3, 2020Â CategoriesCentOS,Â Fedora,Â Linux Commands,Â Linux Distros,Â Monitoring Tools,Â RedHatÂ 18 Comments Â netstatÂ (network statistics) is a command line tool for monitoring network con...

Linux Linux Network Statistics Tools / Commands

Linux Network Statistics Tools / Commands Author:Â Vivek GiteÂ Last updated:Â October 31, 2012Â 8Â comments How do I find out the current network interface throughput statistics on Linux (CentOS or Debian based distro)? How do I see current kernel snm...

Modifying the inode count for an ext2/ext3/ext4 file system

Modifying the inode count for an ext2/ext3/ext4 file system UpdatedÂ August 22 2019 at 12:19 AMÂ -Â EnglishÂ If you run low or completely exhaust the available inodes (index nodes) on your ext2/ext3/ext4 file system, you will seeÂ No space left on d...

awk printf

https://riptutorial.com/awk$$$$$ MATH: $$$$$ Find the remainder of 1 number divided by another use "%" -->>> echo 27 5 | awk '{print $1 % $2}' -->> 2 Comparisons: -->>> echo 4 5 | awk '{if ($1 < $2...

How to disable SSH cipher/ MAC algorithms for Linux and Unix

How to disable SSH cipher/ MAC algorithms for Linux and Unix HowtTosÂ /Â November 04, 2019Â /Â By:Â ayildirim Contents Step 1: Check existing configuration Step 2: Edit SSHD Configuration Step 3: Check the new configuration Some of the security con...

Secure Secure Shell

Secure Secure Shell 2015-01-04 crypto, nsa, and ssh You may have heard that the NSA can decrypt SSH at least some of the time. If you have not, then read theÂ latest batch of Snowden documentsÂ now. All of it. This post will still be here when you f...

How To Ping Specific Port Number

Pinging portsÂ 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...

Using grep to find string in files

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 â different files, anyway, that’s an example, t...

Linux RAID Mdadm Cheat Sheet

Linux RAID Mdadm Cheat Sheet MdadmÂ is the modern tool most Linux distributions use these days to manageÂ software RAIDÂ arrays; in the pastÂ raidtoolsÂ was the tool we have used for this. This cheat sheet will show the mostÂ common usages of mdadmÂ to mana...

Securing /tmp and shm partitions

Securing /tmp and /dev/shm is a nice practice. Â 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 /...

20 IPtables Examples For New SysAdmins

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...

Improve security with polyinstantiation

If you’re concerned about protecting world-writeable shared directories such as /tmp or /var/tmp from abuse, a LinuxÂ® Pluggable Authentication Module (PAM) can help you. The pam_namespace module creates a separate namespace for users on your s...

Install OpenVPN On CentOS / RHEL 7

Security is most important aspect in internet. Outsiders can monitor internet traffic between your computer and the web. Here the importance ofÂ VPNÂ comes. VPN, or virtual private network, is a secure method of connecting remote internet resources tog...

Tip: SSD and Linux. Enable TRIM and check if it works

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...

How to maximise SSD performance with Linux

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 ...

Learn how to align an SSD on Linux

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...

Tips to Solve Linux & Unix Systems Hard Disk Problems

Want to diagnose corrupt disk issues on a server? Want to find out why you are getting âdisk fullâ 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 ...

Set Up SSH Tunneling on a Linux / Unix / BSD Server To Bypass NAT

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...

Top 20 OpenSSH Server Best Security Practices ssh linux aix

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...

How to Migrate from RHEL 8 to CentOS 8

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...

Migrate a Linux System from Red Hat Enterprise to CentOS

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.Â If you are planning in ...

linux aix Killing a process and all of its descendants

Killing a process and all of its descendants Written byÂ @igor_sarcevicÂ onÂ 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...

linux ssh How to Hide the OpenSSH Version Details when Telnet to Port 22

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...

linux ssh Remotely Initiated Reverse SSH Tunnel

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.Â Cron is used on the server to maintain a connection from the hidden remote server...

Linux ssh Hide OpenSSH Version Banner

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...

6 easy steps to setup offline two factor authentication in Linux

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...

CentOS / RHEL 7 : Configuring an NFS server and NFS client Linux NFS

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 â NFSv3 and NFSv4. NFS server and RPC processes starting the ...

Using renice and taskset to manage process priority and CPU affinity with Linux OEL 6.4

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...

chrt command: Set / Manipulate Real Time Attributes of a Linux Process

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 ...

Fix rpmdb: Thread died in Berkeley DB library

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...

Linux An introduction to swap space on Linux systems

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)Â Feed 179 up 5 comments Image by :Â Opensource.com x Subscribe now ...

Yum Update: DB_RUNRECOVERY Fatal error, run database recovery

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...

systemd Auto-restart a crashed service in systemd

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...

Creating SWAP partition using FDISK & FALLOCATE commands

Creating SWAP partition using FDISK & FALLOCATE commands by Shusain Â· Published April 18, 2019 Â· Updated April 18, 2019 Â Swap-partitionÂ holds the memory which is used in case the physical memory (RAM) is full . When RAM capacity has been uti...

How to create stunnel with systemd? stunnel

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...

Linux Audit The Linux security blog about Auditing, Hardening, and Compliance lynis

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...

Testing TLS/SSL encryption

Â 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...

logrotate Log Rotate Configuration

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...

logrotate How log rotation works with logrotate

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...

logrotate Understanding logrotate utility

Understanding logrotate utility Last updated on: 2019-12-20 Â 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...

Logrotate Example for Custom Logs

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 inÂ /var/www/example.com/logs You can put following inÂ /etc/logrotate.d/nginx /var/...

python learning

https://automatetheboringstuff.com/ Â Python Tutorial: OS Module - Use Underlying Operating System Functionality: https://www.youtube.com/watch?v=tJxcKyFMTGo Â Â Â https://www.cs.usfca.edu/~galles/visualization/Algorithms.html Â https://runestone.aca...

How to Configure ‘FirewallD` in RHEL/CentOS 7 and Fedora 21

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...

Linux / UNIX: Run Command a Number of Times In a Row

Linux / UNIX: Run Command a Number of Times In a Row last updated November 27, 2017 in Categories BASH Shell, Linux, UNIX Â How do I run âfooâ command 10 times (or n times) under Linux or UNIX like operating systems? You can use bash shell loop (...

SSH ProxyCommand example: Going through one host to reach another server

SSH ProxyCommand example: Going through one host to reach another server last updated May 17, 2015 in Categories Linux, OpenBSD, UNIX Â How do I use and jump through one server to reach another using ssh on a Linux or Unix-like systems? Is it poss...

Applescript: Run or Call a Shell Script

Applescript: Run or Call a Shell Script last updated January 15, 2017 in Categories Mac OS X, Programming, UNIX Â 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...

socat: Linux / UNIX TCP Port Forwarder

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...

How to run command or code in parallel in bash shell under Linux or Unix

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 Â How do I run commands in parallel in a bash she...

How To Run Multiple SSH Command On Remote Machine And Exit Safely

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 Â I have a backup sync program on lo...

RHEL7 slow ssh login

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 versiÃ³n: vi /etc/ssh...

How to recover error - Audit error: dispatch err (pipe full) event lost

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...

How to stop and disable auditd on RHEL 7

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...

7 Tips – Tuning Command Line History in Bash

7 Tips â Tuning Command Line History in Bash Posted on Tuesday December 27th, 2016by admin Â 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...

Use Fail2ban to Secure Your Server

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...

18 Quick ‘lsof` command examples for Linux Geeks

lsofÂ is a command line utility for all Unix and Linux like operating systems to check âlist of open filesâ The name âlsofâ is itself derived from this functionality. lsof command is mainly used to retrieve information about files that are opened by v...

RHEL7: How to get started with Firewalld.

Note: This is anÂ RHCSA 7 exam objective and anÂ RHCE 7 exam objective. Presentation Firewalld is the new userland interface inÂ RHEL 7. It replaces theÂ iptablesÂ interface and connects to theÂ netfilter kernel code. It mainly improves the security rules ...

Super Grub2 Disk

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. Â Super Grub2 Disk 2.01 rc2 Main Menu Tour Here there is a little video tour in order to discover most of Supe...

10 nmap Commands Every Sysadmin Should Know

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 Â Recently I was compiling a list of Linux commands that every...

8 Vim Tips And Tricks That Will Make You A Pro User

Brief: In this article, I’ll show you some of my favorites Vim tricks with practical examples.Â 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...

3 Ways to Check Linux Kernel Version in Command Line

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...

Easily Find Bugs In Shell Scripts With ShellCheck

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...

Check Detailed CPU Information In Linux With CoreFreq [Advanced]

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...

Tilix: Advanced Tiling Terminal Emulator for Power Users

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...

Easily Monitor CPU Utilization in Linux Terminal With Stress Terminal UI

Brief: Monitoring CPU utilization in Linux becomes a bit better with Stress Terminal UI.Â For we terminal lovers, the more terminal tools, the better. Â I’ve covered a number of terminal tools before, including music player, file browser. Today,...

Terminal based "The Matrix" like implementation

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 ...

Fake A Hollywood Hacker Screen in Linux Terminal linux FUN

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 asciiÂ text, di...

20 Linux Command Tips and Tricks That Will Save You A Lot of Time linux

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...

Monitoring bezpieczeństwa Linux: integracja auditd + OSSEC cz. I

ArtykuÅ poÅwiÄcony jest integracji dwÃ³ch znanych i sprawdzonych narzÄdzi opensource do monitoringu bezpieczeÅstwa: oprogramowania do audytu zmian w systemie Linux (auditd) i Host IDS OSSEC. Celem artykuÅu jest poznanie ograniczeÅ i wykorzystanie zale...

Understanding System auditing with auditd

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...

Learn Linux System Auditing with Auditd Tool on CentOS/RHEL

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...

How To Use the Linux Auditing System on CentOS 7

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...

What Is /dev/shm And Its Practical Usage

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...

Manage SSH Key File With Passphrase

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...

Linux Proxy Server Settings – Set Proxy For Command Line

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, ...

Open SSL Encrypt & Decrypt Files With Password Using OpenSSL

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...

Open SSL Creating Certificate Signing Request — CSR Generation

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...

Open SSL HowTo: Decode SSL Certificate

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...

SSL HowTo: Decode CSR

Moving SSL Certificate from IIS to Apache

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...

OpenSSL: Find Out SSL Key Length – Linux Command Line

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...

OpenSSL: Check SSL Certificate Expiration Date and More

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...

HowTo: Create CSR using OpenSSL Without Prompt (Non-Interactive)

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...

OpenSSL: Check If Private Key Matches SSL Certificate & CSR

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...

How To: Create Self-Signed Certificate – OpenSSL

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 ...

HowTo: Send Email from an SMTP Server using the Command Line

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’ ...

HowTo: Retrieve Email from a POP3 Server using the Command Line

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...

Check a Website Availability from the Linux Command Line

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...

Telnet – Send GET/HEAD HTTP Request

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 â is connect to some web server and verify its health by checking the response code in HTTP head...

SSH: Execute Remote Command or Script – Linux

to ROCK? Start a GUI (graphical) application on a remote Linux workstation over SSH! Read more â Example Execute the local script.sh on the remote server: $ ssh root@192.168.1.1 'bash -s' < script.sh

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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 ...

RHEL : How to deal with “CLOSE_WAIT” and “TIME_WAIT” connection

RHEL : How to deal with âCLOSE_WAITâ and âTIME_WAITâ connection by Ramdev Â· Published March 15, 2014 Â· Updated July 2, 2015 Â CLOSE_WAIT is the state for the TCP connection after the remote side has requested a shut down(FIN), and the TCP conn...

HowTo: Kill TCP Connections in CLOSE_WAIT State

HowTo: Kill TCP Connections in CLOSE_WAIT State Posted on Tuesday December 27th, 2016by admin Â 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...

sed Delete / Remove ^M Carriage Return (Line Feed / CRLF) on Linux or Unix

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...

How to remove CTRL-M (^M) characters from a file in Linux

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...

Extending Linux LVM partitions script

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 âvirtualâ if it’s a VM) storage...

Script to Offline and Remove A Disk In Linux

This script will offline and remove a hard drive from your Linux machine. Â That doesn’t mean it physically pulls it out of your server

HowTo: Find Out Hard Disk Specs / Details on Linux

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 Â Can you tell me a Linux command to find out information about my hard...

how to list all hard disks in linux from command line

how to list all hard disks in linux from command line Â 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...

CentOS / RHEL : How to move a Volume Group from one system to another

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 âdata_vgâ from one system to another. The logical volume from this volume group is ...

Linux LVM recovery

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...

How to use yum-cron to automatically update RHEL/CentOS Linux 6.x / 7.x

The yum command line tool is used to install and update software packages under RHEL / CentOS Linux server. I know how to apply updates usingÂ yum update command line, but I would like to use cron to update packages where appropriate manually. How do ...

Method 2 – Use shell scripts How to install yum cron on a CentOS/RHEL 6.x/7.x

Method 2 â 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...

LOGROTATE – ARCHIWIAZACJA LOGÓW

RosnÄce logi na dysku potrafiÄ zniechÄciÄ kaÅ¼dego administratora do logÃ³w. PomocÄ tutaj okazuje siÄ program Logrotate ktÃ³ry pozwala w Åadny sposÃ³b administrowaÄ logami. Â Konfiguracja programu odbywa siÄ na dwa sposoby. Opcje globalne oraz niezbÄdne ...

INSTALACJA MIB SNMP W SYSTEMIE CENTOS/RHEL 6

Zacznijmy od poczÄtku.Co to jest MIB? Jest to skrÃ³t od Management Information Base, a sam MIB jest prostÄ bazÄ w ktÃ³rej sÄ zapisane informacje o obiektach, a kaÅ¼dy obiekt to jakaÅ informacja.MIB sÄ wykorzystywane przez SNMP, za pomocÄ ktÃ³rego moÅ¼na z...

KONTO SFTP Z CHROOTEM Z UŻYCIEM OPENSSH-SERVER NA CENTOS/RHEL6

Konta SFTP-only moÅ¼emy chcieÄ uÅ¼yÄ, gdy mamy zainstalowany na serwerze SSH (prawie zawsze) i udostÄpniamy daneÂ innemu systemowi, ktÃ³ry loguje siÄ i pobiera je (i ewentualnie usuwa), a nie chcemy instalowaÄ dodatkowej aplikacji jak FTPd czy HTTPd. Za...

SPRAWDZONA KONFIGURACJA RSYSLOG I LOGROTATE, JAKO ZEWNĘTRZNEGO SERWERA SYSLOG

rsyslog jest domyÅlnÄ aplikacjÄ logujÄcÄ w systemach RHEL6 /CentOS 6. Tak jak i inne syslogi, funkcjonuje w oparciu o pliki lokalne oraz zewnÄtrznie o domyÅlne porty TCP i/lub UDP 514. To, czy bÄdziemy uÅ¼ywaÄ TCP, czy UDP, zaleÅ¼y od nas, odpowiada za...

How log rotation works with logrotate

logrotate - rotates, compresses, and mails system logs.

NAME logrotateÂ - rotates, compresses, and mails system logs. SYNOPSIS logrotate [-dv] [--force] [-s|--state statefile] config_file .. DESCRIPTION logrotateÂ is designed to ease administration of systems that generate large numbers of log files. It a...

Understanding logrotate utility part 1

Last updated on: 2016-06-29 Â 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 ...

Sample logrotate configuration and troubleshooting part 2

Last updated on: 2015-12-31 Â Authored by: Jered Heeschen Applying knowledge In theÂ previous articleÂ 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...

HowTo: The Ultimate Logrotate Command Tutorial with 10 Examples

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 UNIXÂ logrotateutility. Rotate the log file when file size reaches a specific size Continue to ...

Tcpdump Examples Linux

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...

Increase A VMware Disk Size (VMDK) Formatted As Linux LVM without rebooting

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 ...

Lsyncd: live file syncronization across multiple Linux servers

Lsyncd is a tool I discovered a few weeks ago. It is a synchronization server based primarily on Rsync.Â It is a server daemon that runs on the âmasterâ server, and it can sync / mirror any file or directory changes within seconds into your âslavesâ s...

How to Install and use Lsyncd on CentOS 7 / RHEL 7 rsync

Lsyncd stands for âLive Syncing Daemonâ, 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 ...

How to Synchronize Directories Using Lsyncd in Linux

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.Â Â Lsyncd is a light-weight live mirror solution that is comparatively easy to install w...

12 Linux Rsync Options in Linux Explained

In this article, I would show the different rync options to sync file/directories to the destination server.Â The main advantages of the rsync are: Speed: Initially copies the whole content between local and remote system. Next, it transfers only the ...

10 Linux rsync Examples to Exclude Files/Directories

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...

Exclude multiple files and directories with rsync

Exclude multiple files and directories withÂ 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...

6 rsync Examples to Exclude Multiple Files and Directories using exclude-from

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...

How to Register and Enable Red Hat Subscription, Repositories and Updates for RHEL 7.0 Server

After the last tutorial on minimal installation ofÂ 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...

SYS: Configure a local repository. local repo

SYS: Configure a local repository. Last updated onÂ October 6, 2018Â (11,511 views) -Â CertDepotÂ —Â 29 Comments â Share this link 0 0 Â Create a directory where packages will be stored: # mkdir /repo Two options: mount the distr...

Using Official Redhat DVD as repository

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...

Need to set up yum repository for locally-mounted DVD on Red Hat Enterprise Linux 7

Need to set up yum repository for locally-mounted DVD on Red Hat Enterprise Linux 7 Â SOLUTION VERIFIEDÂ - UpdatedÂ February 27 2018 at 10:15 PMÂ -Â EnglishÂ Environment Red Hat Enterprise Linux 7 Issue How to set up yum repository to use locally-...

Enabling or disabling a repository using Red Hat Subscription Management

Enabling or disabling a repository using Red Hat Subscription Management Â SOLUTION VERIFIEDÂ - UpdatedÂ October 9 2017 at 2:10 PMÂ -Â EnglishÂ Environment Red Hat Enterprise Linux (RHEL) 5.7 or higher, 6.1 or higher Red Hat Subscription Management ...

Find All Large Files On A Linux System

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. Â Â Before getting started, we suggest youÂ Learn Linux B...

How To Find Largest Top 10 Files and Directories On Linux / UNIX / BSD find

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. TheÂ -sizeÂ switch explained: -size n[cwbkMG] Fi...

Linux Find Large Files

Linux Find Large Files last updatedÂ December 17, 2008Â inÂ CategoriesBASH Shell,Â CentOS,Â Debian / Ubuntu,Â Fedora Linux,Â File system,Â Linux,Â RedHat and Friends,Â Ubuntu Linux Q.Â How do I find out all large files in a directory?A.Â There is no single co...

Automatic YUM Updates with Yum-cron

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? Â The yum-cron is an optional packag...

Install Security Patches or Updates Automatically on CentOS and RHEL

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 ...

How to enable automatic security updates on CentOS 7 with yum-cron

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...

YUM CRON Enabling automatic updates in Centos 7 and RHEL 7

In previous posts we’ve seen how toÂ Enable automatic security update in Debian/UbuntuÂ 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...

YUM CRON RHEL7: Configure automatic updates.

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 ...

CentOS / RHEL : Configure yum automatic updates with yum-cron service

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,...

Cron YUM How to use yum-cron to automatically update RHEL/CentOS Linux

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 ...

What is yum-cron ?

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...

20 Linux YUM (Yellowdog Updater, Modified) Commands for Package Management YUM

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...

YUM How to use yum command on CentOS/RHEL

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 ...

15 Linux Yum Command Examples – Install, Uninstall, Update Packages

15 Linux Yum Command Examples â 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 ...

RHEL7: Configure automatic updates.

Presentation TheÂ yum-cronÂ package provides a convenient way to check for, download and apply updates automatically. Installation procedure Install theÂ yum-cronÂ package: # yum install -y yum-cron Start theÂ yum-cronÂ service: # systemctl start yum-cron ...

Enabling automatic updates in Centos 7 and RHEL 7

In previous posts we’ve seen how toÂ Enable automatic security update in Debian/UbuntuÂ and inÂ 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...

How to use yum-cron to automatically update RHEL/CentOS Linux

How to use yum command on CentOS/RHEL

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 commandÂ was part of RHEL v4.x or older version. You ne...

red hat 7 tmpfiles service

/etc/tmpfiles.d/Â 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...

How to mount software RAID1 member using mdadm

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 *...

How to deal with dmesg timestamps

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...

How to accurately determine when the system was booted

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...

How to convert RAW image to VDI and otherwise

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...

Linux PAM configuration that allows or deny login via the sshd server

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...

Red Hat Enterprise Linux - Allow Root Login From a Specific IP Address Only

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...

Top 20 OpenSSH Server Best Security Practices - good article

Top 20 OpenSSH Server Best Security Practices last updatedÂ May 16, 2018Â inÂ CategoriesCentOS,Â Debian Linux,Â fedora linux,Â FreeBSD,Â Gentoo Linux,Â Howto,Â Linux,Â Networking,Â package management,Â RedHat/Fedora Linux,Security,Â Suse Linux,Â Sys admin,Â Ubuntu...

Turbocharge PuTTY with 12 Powerful Add-Ons – Software for Geeks #3

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...

Top 25 Best Linux Performance Monitoring and Debugging Tools

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 ...

Linux / UNIX: DNS Lookup Command

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...

10 Linux DIG Command Examples for DNS Lookup

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...

10 Linux nslookup Command Examples for DNS Lookup

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...

List DNS records, nameservers of a domain from command line

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 > Â If you want to find out...

Linux nslookup Command Examples for DNS Lookup

Linux Cluster Tutorial

https://www.alteeve.com/w/AN!Cluster_Tutorial_2#What.27s_New.3F

linux manual tools

Main Page Â 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...

Stunnel Setup

Stunnel Setup Â 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 Â Overview Stunnel is a SSL proxy designe...

Tunnel SSH Connections Over SSL Using ‘Stunnel` On Debian 7 / Ubuntu 13.10

Tunnel SSH Connections Over SSL Using ‘Stunnel’ On Debian 7 / Ubuntu 13.10 By SK - December 30, 2013 6877 Â stunnel is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote serve...

Setup SSL Tunnel Using Stunnel on Ubuntu

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...

stunnel Howto A Guide to create SSL access to a HTTP-only webserver with stunnel

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. Â fm@susie:/home/devel> zcat ../software/stunnel-4.15.tar.gz ...

HP-UX - Stunnel Configuration

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 ...

Installing and Configuring stunnel on CentOS 6

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...

HOWTO: Use SSL/port 465 in smarthost stunnel

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...

Deskshare TLS over Stunnel

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...

Using stunnel and TinyProxy to obfuscate HTTP traffic

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...

How To Set Up an SSL Tunnel Using Stunnel on Ubuntu

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 ...

Setting up encrypted tunnel using stunnel

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...

stunnel bacula

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 ...

stunnel basics and pki standards

stunnel basics and pki standards Â # 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...

stunnel: Authentication

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 ...

debian Debian/Ubuntu Linux: Find If Installed APT Package Includes a Fix/Patch Via CVE Number

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 ...

debian How to check Debian CVE status using python script

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...

debian How to Upgrade Debian 8 Jessie to Debian 9 Stretch

How to Upgrade Debian 8 Jessie to Debian 9 Stretch Posted by Jarrod on June 17, 2017 Leave a comment (16) Go to comments Â Debian 9 Stretch was released as the latest stable version of the Linux Debian operating system today. While you can install...

debian Install a newer kernel in Debian 9 (stretch) stable

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...

Linux Chage Command to Set Password Aging for User

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 theÂ ‘-l’ option to view their...

How to manage Linux password expiry with the chage command

As a Linux admin, you're probably accustomed toÂ passwd,Â chown,Â chmod, andÂ chgrp...all commands for managing various elements of user accounts, files, and folders. There is another command that all Linux administrators must know:Â chageÂ (think of ...

Manage Linux Password Expiration and Aging Using chage

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.Â It’s the system adm...

An easier way to manage disk decryption at boot with Red Hat Enterprise Linux 7.5 using NBDE

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...

RHEL7: Create and configure LUKS-encrypted partitions and logical volumes to prompt for password and mount a decrypted file system at boot.

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...

linux unix aix banner /etc/issue

### WARNING ### WARNING ### WARNING ### WARNING ### WARNING ### WARNING ### Â Â This is a private computer system.Â This computer system, including all Â Â related equipment, networks, and network devices (specifically including Â Â Internet access) is...

OEL 7 – How to disable IPv6 on Oracle Linux 7

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...

Linux Network (TCP) Performance Tuning with Sysctl

Linux Network (TCP) Performance Tuning with Sysctl Â 16UdostÄpnij Â 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...

Linux Kernel /etc/sysctl.conf Security Hardening

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...

Kernel sysctl configuration file for Linux

# 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...

10 Linux cryptsetup Examples for LUKS Key Management (How to Add, Remove, Change, Reset LUKS encryption Key)

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...

WatchDog watchdog.sh script for checking server running

#!/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...

watchdog How to restart a process out of crontab on a Linux/Unix

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 Â I am a new Linux user and not familiar with crontab syntax. How do I use a cron job to resta...

Watchdog script to keep an application running

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...

Expand or grow a file system on a Linux VMWare VM without downtime

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...

Use inotify-tools on CentOS 7 or RHEL 7 to watch files and directories for events

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 ...

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A Quick and Practical Reference for tcpdump

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...

12 Tcpdump Commands – A Network Sniffer Tool

12 Tcpdump Commands â A Network Sniffer Tool by Narad Shrestha | Published: August 20, 2012 | Last Updated: September 13, 2012 Â Â Download Your Free eBooks NOW - 10 Free Linux eBooks for Administrators | 4 Free Shell Scripting eBooks Â Â In our pr...

tcpdump usage examples

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...

tcpdump

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...

Using IOzone for Linux disk performance analysis

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...

Linux: Disks diagnostic using smartctl

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...

Linux: how to monitor the nofile limit

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 â or in /etc/limits.d â that is displayed by ‘ulimit -n&rs...

FIO (Flexible I/O) – a benchmark tool for any operating system

I have just attended an interesting session heldÂ by Martin Nash (@mpnsh) at UKOUG 14 â Liverpool: âThe least an Oracle DBA Should Know about Linux Administrationâ . During this session I had the opportunity to discover some interesting commands ...

Linux – How to check the exit status of several piped commands

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...

How to do a Filesystem Resize (ext3/ext4) on Redhat running on VMware

A filesystem resize can be done in several ways, online, offline, with LVM2 or without LVM2. Â 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...

List usernames instead of uids with the ps command for long usernames

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...

Linux – Securing your important files with XFS extendend attributes

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 -...

OEL 7 – How to disable IPv6 on Oracle Linux 7 – Follow Up

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/Â then you have already IPv6 s...

Oracle Linux 7 – How to audit changes to a trusted file such as /etc/passwd or /etc/shadow

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 ...

How to enable Proxy Settings for Yum Command on RHEL / CentOS Servers

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 Â· Published January 30, 2017 Â· Updated August 2, 2017 Â In most of the data center direct...

What UUIDs can do for you

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...

How to retrieve and change partition`s UUID Universally Unique Identifier on linux

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 ...

Get UUID of Hard Disks [Update]

Short Tip: Get UUID of Hard DisksÂ [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...

UUIDs and Linux: Everything you ever need to know [Update]

UUIDs and Linux: Everything you ever need to knowÂ [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...

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http://vsphere-land.com/vinfo/free-tools Free Tools Â Â 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...

LUKS dm-crypt/Device encryption GUIDE

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...

Index » Community Contributions » System encryption using LUKS and GPG encrypted keys for arch linux

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 ...

How to encrypt a partition with DM-Crypt LUKS on Linux

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...

How to encrypt a partition using LUKS?

How to encrypt a partition using LUKS? Â 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 ...

How To: Linux Hard Disk Encryption With LUKS [ cryptsetup Command ]

How To: Linux Hard Disk Encryption With LUKS [ cryptsetup Command ] Â Linux encryption methods There are two methods to encrypt your data: #1: Filesystem stacked level encryption eCryptfs â It is a cryptographic stacked Linux filesystem. eCryptfs st...

LUKS List available methods of encryption for LUKS

$ 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...

high swap space utilization in LINUX

Â high swap space utilization in LINUX This morning, I got a ticket that one LINUX machine is about to consume all its swap spaceâ¦.. I addressed this ticket very much like I would do it if this was AIX â only the commands to resolve this situati...

SSH Essentials: Working with SSH Servers, Clients, and Keys

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...

O`Reilly`s CD bookshelf

https://docstore.mik.ua/orelly/bookshelfs.html Â The Java Reference Library, version 1.3 The Java Enterprise CD Bookshelf, Version 1.0 The Perl CD Bookshelf, version 1.0 ...

Using Kerberos security with Server for NFS

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 ...

Epoch & Unix Timestamp Conversion Tools

The current Unix epoch time isÂ 1529656113 Â Convert epoch to human readable date and vice versa Â [batch convert timestamps to human dates] GMT: Friday, 22 June 2018 07:40:23Your time zone: piÄtek, 22 czerwca 2018 09:40:23 GMT+02:00 DST Yr Mon D...

Do you Know These 5 Use of V$session View ?

Do you Know These 5 Use of V$session View ? Â Â V$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...

List of 10 Must Know Oracle Database Parameters for Database Administrator

List of 10 Must Know Oracle Database Parameters for Database Administrator Â Â 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...

What is OS Watcher Utility and How to use it for Database Troubleshooting ?

What is OS Watcher Utility and How to use it for Database Troubleshooting ? Â Â 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...

How to Analyze or Read OS Watcher Output in three easy steps -- With Example ?

How to Analyze or Read OS Watcher Output in three easy steps -- With Example ? Â Â 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 ...

Top 4 Reasons for Node Reboot or Node Eviction in Real Application Cluster (RAC) Environment

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...

A tcpdump Tutorial and Primer with Examples

Â A tcpdump Tutorial and Primer with Examples Created: January 4, 2004 | Updated: October 30, 2017 Â Why tcpdump? Basics Examples Basic Communication Specific Interface Raw Output View Find Traffic by IP Seeing Packet Contents with Hex Output ...

Procedura powiekszania OCFS2 online

ProcedurÄ wykonujemy po powiÄkszeniu LUN na macierzy dyskowej Â Zawsze wykonujemy backup file systemu, ktÃ³ry powiÄkszamy Â Wykonujemy komendÄ df âkv lub Â df âakP Â (lepiej formatuje wynik POSIX) lub df -h -T | grep ocfs2 (tylko fs ocfs2) Â df -h -...

How to schedule crontab in Unix Operating Systems

How to schedule crontab in Unix Operating Systems. Â 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...

Linux Health Check Commands

Linux Health Check Commands Â 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 ...

Linux - How to shutdown or reboot

Linux - How to shutdown or reboot Â 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...

Linux - How to unlock and reset user`s account

Linux - How to unlock and reset user's account Â 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...

Linux - Cannot login from remote console but can access via ssh

Linux - Cannot login from remote console but can access via ssh Â 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...

Linux - How to get IP and MAC address of ethernet adapter in Linux

Linux - How to get IP and MAC address of ethernet adapter in Linux Â 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...

Linux - How to get network speed and statistic of ethernet adapter in Linux

Linux - How to get network speed and statistic of ethernet adapter in Linux Â Question : How to get network speed of ethernet adapter in Linux. Answer : "ethtool " command can be used to get network speed of specific ethernet card in Linu...

Linux - How to monitor CPU usage

Linux - How to monitor CPU usage Â 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...

Linux - How to monitor memory usage

Linux - How to monitor memory usage Â 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 ...

Linux - How to get CPU information

Linux - How to get CPU information Â 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 : [...

Linux - How to get Memory information

Linux - How to get Memory information Â 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...

How to automate SSH login with password? ssh autologin

How to automate SSH login with password? Â 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...

Linux - How to perform I/O performance test with dd command

Linux - How to perform I/O performance test with dd command Â Question : How to perform I/O performance test in Linux to find r/w speed? Answer : Â It can be achieved using dd command. Example to test write speed : 1. Go to the directory location whe...

Red Hat ADDING SWAP SPACE

7.2.Â 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 ...

How To Add Swap Space on Ubuntu 16.04

How To Add Swap Space on Ubuntu 16.04 PostedApril 25, 2016Â 396.9kviewsÂ LINUX BASICSÂ UBUNTUÂ UBUNTU 16.04 Justin Ellingwood Introduction One of the easiest way of increasing the responsiveness of your server and guarding against out-of-mem...

Linux Add a Swap File – HowTo

Linux Add a Swap File â HowTo Posted onMay 18, 2006inÂ CategoriesDebian / Ubuntu,Â File system,Â Linux,Â RedHat and Friends,Â Suse,Ubuntu LinuxÂ last updated May 3, 2017 Â Ineed additional swap space to improve my Linux server/desktop system performance...

Create a Linux Swap File

Create a Linux Swap File Last updated on: 2015-08-19 Â 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 ...

How To Create a Linux Swap File

How To Create a Linux Swap File byÂ Aaron KiliÂ | Published: June 15, 2017 | Last Updated: June 15, 2017 Â Â Â Download Your Free eBooks NOWÂ -Â 10 Free Linux eBooks for AdministratorsÂ |Â 4 Free Shell Scripting eBooks Â Â In this article, we will explain...

Using etckeeper with git

Using etckeeper with git on Ubuntu by Jeremy L. Gaddis on February 18, 2011 Â· 5 comments in System Administration Â Â Â Though I think we would all agree that it’s important, the unfortunate fact is that myself and other members o...

Red Hat Cluster Tutorial

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...

RHCS6: Debug and test multicast traffic between two hosts

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...

RHCS6: Reduce a Global Filesystem 2 (GFS2)

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 :)

RHCS6: Mirror/unmirror a GFS2 volume

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...

RHCS6: Show/Add GFS2/GFS journals

RHCS: Show/Add GFS2/GFS journals # Tested on RHEL 6/gfs2 and RHEL 5/gfs# GFS2 -------------------------------# Showing journals of a gfs2 filesystemgfs2_tool journals /Â Â journal2 - 128MBÂ Â journal3 - 128MBÂ Â journal1 - 128MBÂ ...

RHCS6: Extend an existing Logical Volume / GFS2 filesystem

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 /sharedfsÂ Â FilesystemÂ Â Â Â Â Â Â Â Â Â Â SizeÂ Used Avail Use% Mounted onÂ Â /dev/mapper/gfsv...

RHCS6: Create a new Logical Volume / Global Filesystem 2 (GFS2)

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, ...

RHCS6: Quorum disk and heuristics

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...

RHCS6: Clustered LVM

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�...

RHCS6: Basic operations on clustered services

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: QuorateÂ Member NameÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ...

RHCS6: Luci - the cluster management console

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...

RHCS6: Install a two-node basic cluster

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...

RHCS6: `fencing` basics

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#...

RHCS: Configure an active/backup pacemaker cluster

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 #Â Â Â Â nodes and [ONE] indicates that one needs to run it only on one of th...

RHCS: Install a two-node basic cluster

RHCS: Install a two-node basic cluster # Tested on CentOS 7 Â # Notes mainly from http://clusterlabs.org/pacemaker # Note: For the commands here after, [ALL] indicates that command has to be run on the two #Â Â Â Â nodes and [ONE] indicat...

ZPOOL: Remove an existing zpool

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=`...

ZPOOL: Verify/change properties of a zpool

ZPOOL: Verify/change properties of a zpool # Tested on RHEL 6 & 7ZPOOL=my_pool# Check the properties of the zpoolzpool get all $ZPOOLÂ Â NAMEÂ Â Â Â PROPERTYÂ Â Â Â Â Â VALUEÂ Â Â Â Â Â SOURCEÂ Â my_poolÂ sizeÂ Â Â Â Â Â Â Â Â Â 19.9GÂ Â Â Â Â Â -Â Â my_poolÂ capacityÂ Â ...

ZPOOL: Detach a submirror from a mirrored zpool

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...

ZPOOL: Add a mirror to a concat zpool

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 $POOLNAMEÂ Â Â Â poo...

ZPOOL: Grow a zpool by adding new device(s)

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.# --------------------------------------------------------------------------------...

ZPOOL: Create a new zpool for zfs filesystems

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...

ZFS: Snapshots and clones on zfs filesystems

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...

ZFS: Remove an existing zfs filesystem

ZFS: Remove an existing zfs filesystem # Tested on RHEL 6 & 7# Choose the F.S. to removezfs listÂ Â NAMEÂ Â Â Â Â Â Â Â Â Â USEDÂ AVAILÂ REFERÂ MOUNTPOINTÂ Â c_poolÂ Â Â Â Â Â Â Â 349MÂ 19.2GÂ Â Â 30KÂ /c_poolÂ Â c_pool/zfs01Â Â 349MÂ Â 675MÂ Â 349MÂ /zfs01Â Â c_po...

ZFS: Verify/change properties of a zfs filesystem

ZFS: Verify/change properties of a zfs filesystem # Tested on RHEL 6 & 7ZPOOL=c_poolZFSFS=zfs01# Check the properties of the filesystemzfs get all $ZPOOL/$ZFSFSÂ Â NAMEÂ Â Â Â Â Â Â Â Â PROPERTYÂ Â Â Â Â Â Â Â Â Â Â Â Â VALUEÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â SOURCEÂ Â c_pool/zf...

ZFS: Grow/Shrink an existing zfs filesystem

ZFS: Grow/Shrink an existing zfs filesystem # Tested on RHEL 6 & 7# Choose the F.S. to resize and verify current sizezfs listÂ Â NAMEÂ Â Â Â Â Â Â Â Â Â USEDÂ AVAILÂ REFERÂ MOUNTPOINTÂ Â c_poolÂ Â Â Â Â Â Â Â 204KÂ 19.6GÂ Â Â 30KÂ /c_poolÂ Â c_pool/zfs01Â Â Â 30K...

ZFS: Create a new zfs filesystem

ZFS: Create a new zfs filesystem # Tested on RHEL 6 & 7# Select the zpool where F.S. will be createdzpool listÂ Â NAMEÂ Â Â Â SIZEÂ ALLOCÂ Â FREEÂ Â Â CAPÂ DEDUPÂ HEALTHÂ ALTROOTÂ Â c_poolÂ 9.94GÂ Â 120KÂ 9.94GÂ Â Â Â 0%Â 1.00xÂ ONLINEÂ -Â Â m_poolÂ 9....

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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,...

LVM: Remove an existing Volume Group

LVM: Remove an existing Volume Group # Tested on RHEL 5, 6 & 7VG=testvgvgdisplay -v $VGÂ Â Â Using volume group(s) on command line.Â --- Volume group ---Â VG NameÂ Â Â Â Â Â Â Â Â Â Â Â Â Â testvgÂ System IDÂ FormatÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â lvm2Â Metadata AreasÂ Â ...

LVM: Reduce an existing Volume Group by removing one of its disks

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"Â Â PV NameÂ Â Â Â Â Â Â Â Â Â Â Â Â Â /dev/sde1Â Â PV NameÂ Â Â Â Â Â Â Â Â Â Â Â Â Â /dev/sde2Â Â P...

LVM: Extend an existing Volume Group by adding a new disk

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...

LVM: Create a new Volume Group

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...

LVM: Reduce SWAP size by removing a Logical Volume

LVM: Reduce SWAP size by removing a Logical Volume # Tested on RHEL 5, 6 & 7# Check current swap volume(s) and its sizeroot@:/#> cat /etc/fstab | grep swap/dev/rvg/swaplvÂ Â Â Â Â Â Â Â swapÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â swapÂ Â Â defaultsÂ Â Â Â ...

LVM: Reduce SWAP size by shrinking existing Logical Volume

LVM: Reduce SWAP size by shrinking existing Logical Volume # Tested on RHEL 5, 6 & 7# Check which is the swap volume and its sizeroot@:/#> cat /etc/fstab | grep swap/dev/rvg/swaplvÂ Â Â Â Â Â Â Â swapÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â swapÂ Â Â de...

LVM: Extend SWAP size by growing existing Logical Volume

LVM: Extend SWAP size by growing existing Logical Volume # Tested on RHEL 5, 6 & 7# Check which is the swap volume and its sizeroot@:/#> cat /etc/fstab | grep swap/dev/rvg/swaplvÂ Â Â Â Â Â Â Â swapÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â swapÂ Â Â defa...

LVM: Extend SWAP size by adding a new Logical Volume

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@:/#> cat /...

LVM: Managing snapshots

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.# ...

LVM: Rename root VG/LV

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:lvsÂ LVÂ Â VGÂ Â Â Â Att...

LVM: Reduce root PV/VG

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...

LVM: Recovering Physical Volume Metadata

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 ...

LVM: Move allocated PE between Physical Volumes

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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...

LVM: Remove a Filesystem / Logical Volume

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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#Â Â Â Â ext2/ext3/ext4 filesystems.# *** As of February 2016, new implementati...

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Inxi – A Powerful Feature-Rich Commandline System Information Tool for Linux

Inxi â A Powerful Feature-Rich Commandline System Information Tool for Linux by Aaron Kili | Published: February 20, 2017 | Last Updated: February 20, 2017 Â Â Download Your Free eBooks NOW - 10 Free Linux eBooks for Administrators | 4 Free Shell Scr...

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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 âinxiâ.Â It is free, open sourc...

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RHEL: Force system to prompt for password in Single User mode

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...

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RHEL: Services basic management - chkconfig

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RHEL: Retrieve and generate a unique SCSI identifier

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RHEL: Allowing users to `su` to "root" / Allowing `root` to login directly to the system using `ssh`

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RHEL: Route network packets to go out via the same interface they came in

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RHEL: Rename a network interface on RHEL 7

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RHEL: Bonding network interfaces

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RHEL: Multipathing basics

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RHEL: Remove existing SAN LUNs

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RHEL: Rebuilding the initial ramdisk image

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RHEL: Displaying/setting kernel parameters - `sysctl`

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RHEL: Building a custom kernel on RHEL 6

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RHEL: Crash kernel dumps configuration and analysis on RHEL 7

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RHEL: Crash kernel dumps configuration and analysis on RHEL 6

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RHEL: Crash kernel dumps configuration and analysis on RHEL 5

RHEL: Crash kernel dumps configuration and analysis on RHEL 5 Apart from this recipe, more information about the configuration can be found inthe file â/usr/share/doc/kexec-tools-*/kexec-kdump-howto.txtâhttps://access.redhat.com/knowledge/docs/...

RHEL: iSCSI target/initiator configuration on RHEL7

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RHEL: iSCSI target/initiator configuration on RHEL6

RHEL: iSCSI target/initiator configuration on RHEL6 # Tested on RHEL 6# iSCSI target configuration# ------------------------------------------------------------------------------------------# Required package: scsi-target-utils# Some documentat...

RHEL: Getting/Setting hardware clock`s time

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RHEL: Change system`s hostname

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RHEL: Checking HBAs

# Tested on RHEL 6# Show the instances of FC ports connected to the pci bus:lspci | grep -i "Fibre"Â Â 07:00.0 Fibre Channel: QLogic Corp. ISP2532-based 8Gb Fibre Channel to PCI Express HBA (rev 02)Â Â 07:00.1 Fibre Channel: QLogic Corp. ISP2532-based ...

RHEL: Adding a boot entry to GRUB/GRUB2 configuration

# 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...

RHEL: GPT/MBR partition tables (using disks larger than 2 TiB)

# 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...

RHEL: Enabling standard ftp/telnet

# 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...

RHEL: Manually encrypting a filesystem with LUKS

# Tested on RHELÂ 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...

RHEL: Reserved space on a ext2/ext3/ext4 filesystem

# 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...

RHEL: Extending the maximum inode count on a ext2/ext3/ext4 filesystem

# 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...

RHEL: Displaying system info (firmware, serial numbers... )

# Tested on RHEL 5, 6 & 7# Network interface cards driver, driver version, firmware version, and bus informationethtool -i eth0Â Â driver: bnx2Â Â version: 2.0.8-rhÂ Â firmware-version: bc 5.2.3 NCSI 2.0.6Â Â bus-info: 0000:03:00.0cat /var/log/dmes...

RHEL: Extending a vmdk (Virtual Machine disk)

# 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...

RHEL: Handling SCSI disks

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RHEL: Back-up/Replicate a partition table

# 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...

RHEL: ACLs basics

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...

RHEL: Reinstalling Boot Loader on the Master Boot Record (MBR)

# 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...

RHEL: Resize/disable /dev/shm filesystem

# 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...

RHEL: Extending a multipath LUN

# 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...

RHEL: Scan and configure new SAN (fibre channel) LUNs

# Tested on RHEL 5 & 6 # Identify host adapters on the systemsystool -c fc_hostÂ Â Class = "fc_host"Â Â Â Â Class Device = "host3"Â Â Â Â Â Â Device = "host3"Â Â Â Â Class Device = "host4"Â Â Â Â Â Â Device = "host4"ls /sys/class/fc_hostÂ Â host3Â host4# Rescan t...

RHEL: Create a local RPM repository

# Tested on RHEL/CentOS 6 & 7# Mount the installation disk and copy packages from /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...

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S kanery do portÃ³w sÄ jak ÅrubokrÄty. Nigdy nie ma ani jednego w pobliÅ¼u kiedy jest najbardziej potrzebny. Z pomocÄ przychodzi powÅoka bash: 1 2 3 4 5 6 7 8 9 10 11 12 #!/bin/bash for a in $(yes scan | head -1024) Â Â do Â Â (( start++ )) Â Â if [...

Netcat shell zabezpieczony hasłem

Prosty skrypt autorstwa Vittorio Milazzo ukazujÄcy sposÃ³b przyznania powÅoki za pomocÄ netcat dopiero po podaniu hasÅa: 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...

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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...

Odpalenie polecenia tylko na jedną godzinę

UÅ¼ycie polecenia timeout do uruchomienia wybranego polecenia na okreÅlony czas dziaÅania: 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)

OpenSSL – sprawdzanie czy klucz pasuje do certyfikatu

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Linux – delete the LUN and remove traces from OS

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. ...

Linux get the list of FC HBA`s and WWPN

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...

Top 10 darmowych i publicznych serwerów DNS

1.Â Google: â 8.8.8.8, 8.8.4.4 2. OpenDNS: â 208.67.220.220, 208.67.222.222 3. Norton ConnectSafe: â 199.85.126.10, 199.85.127.10 4. Comodo Secure DNS: â 8.26.56.26, 8.20.247.20 5. DNS.Watch: â 84.200.69.80, 84.200.70.40 6. VeriSign Public DNS: â 64.4...

How to sort IP addresses in Linux

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....

How to find the largest files and directories in Linux?

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 Â Â Â source: http://www.linuxask.com/questio...

BIND for the Small LAN

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...

Jak ustawić LVM, jak robić snapshoty oraz automatycznie powiększać LV, czyli małe howto

1. Co to jest i do czego sÅuÅ¼y LVM (Logical Volume Manager) pozwala na grupowanie urzÄdzeÅ w wirtualne Volume Group (VG, nie lubiÄ polskich tÅumaczeÅ ;p) z ktÃ³rych potem moÅ¼na tworzyÄ Logical Volume (LV) czyli taki wirtualny odpowiednik partycji dysk...

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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 âvirtualâ if it’s a VM) storage device prior to execution. It will rescan the ...

How setting the TZ environment variable avoids thousands of system calls

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...

Fałszujemy rozpoznania skanerów #1

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W pierwszej czÄÅci pokazaÅem, jak Åatwo za pomocÄ iptables sfaÅszowaÄ nasÅuchujÄce usÅugi. W tym przykÅadzie zajmiemy siÄ technikÄ zwanÄ banner grabbing. Proces ten powoduje, Å¼e skaner przechodzi do warstwy aplikacji i zaczyna zachowywaÄ siÄ, jak kli...

Jak znaleźć najszybszy publiczny serwer DNS w Polsce?

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...

Configuring VLAN interfaces in Linux

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 ...

How do I add ethtool settings to a network device permanently?

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...

“Too many authentication failures” with SSH

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...