Linux Health Check Commands

Linux Health Check Commands

 
This document contains some of the commonly used linux commands when performing health check on a machine running Linux Operating System.

To view overall performance.
[root@myserver]# top

Note:
- By default is will sort processes based on CPU usage. Press "M" to sort based on memory usage.

To view I/O of storage devices.
[root@myserver]# iostat
[root@myserver]# iostat -d  #Display only disk I/O statistics
[root@myserver]# iostat -n  #Display on network storage devices
[root@myserver]# iostat -m  #Display I/O in MB/s
[root@myserver]# iostat 1 3 #Display I/O every second for 3 times


To check CPU usage at interval of 5 seconds for 3 times.
[root@myserver]# sar -u 5 3
Linux (mysever)  09/29/2013

08:31:15 PM       CPU     %user     %nice   %system   %iowait     %idle
08:31:20 PM       all     16.92      0.00      1.48      0.15     81.45
08:31:25 PM       all     14.65      0.00      0.80      0.10     84.45
08:31:30 PM       all     15.85      0.00      2.02      0.07     82.05
Average:          all     15.81      0.00      1.43      0.11     82.65


To check memory and swap utilization in megabytes.
[root@myserver]# free -m
             total       used       free     shared    buffers     cached
Mem:          3735       3567        168          0        270       2221
-/+ buffers/cache:       1075       2659
Swap:         8191         23       8168


To find out top 10 processes consumed the most memory.
The below command will take the output of "ps -aux", sort the memory column which is column 4 from highest value to lowest and output the first 10 results.
[root@myserver]# ps -aux |sort -nrk 4| head -10


To find out top 10 processes consumed the most CPU.
The below command will take the output of "ps -aux", sort the CPU column which is column 3 from highest value to lowest and output the first 10 results.
[root@myserver]# ps -aux |sort -nrk 3| head -10


To check how many network interface configured.
[root@myserver]# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 11:0B:2D:EF:07:30
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:16

eth1      Link encap:Ethernet  HWaddr 12:0B:44:FF:47:DF
          inet addr:192.0.0.1  Bcast:192.0.0.255  Mask:255.255.255.192
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1216011503 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4253525258 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:24


To check speed of eth1.
Settings for eth1:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000ff (255)
        Link detected: yes


To check if all hard mount filesystems are mounted properly issue command "df -h" and cross check with the file /etc/fstab.

[root@myserver]# cat /etc/fstab
[root@myserver]# df -h


To check who is currently logged in.
[root@myserver]# w


To check login history.
[root@myserver]# last


To check current date & time on the server.
[root@myserver]# date


To check current and previous runlevel.
The below output indicate the current runlevel is 3 and previous was 1 [Single user].
[root@myserver]# who -r
run-level 3 Sep 26 06:20 last=S


To check current and previous runlevel.
The below output indicate the current runlevel is 3 and N indicates the runlevel was not change since boot.

[root@myserver]# runlevel
N 3


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.
[root@myserver]# shutdown


To shutdown the Operating System and poweroff.
[root@myserver]# shutdown -h now


To cancel shutdown.
[root@myserver]# shutdown -c


To list services configured.
[root@myserver]# chkconfig --list


To start a service.
[root@myserver]# service nfs start


To view hardware info.
[root@myserver]# dmidecode
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