Linux Administrator Should Know To Use PS Command With Example

Linux System administrator should have very proficient in Linux performance monitoring and tuning. For performance monitoring, Linux system administrator should understand how various Linux component and processes works (like CPU, Memory, I/O, Network) ps (process status) is a command use to display current running processes on Unix operating systems. This command is commonly used for process monitoring. Whenever you feel that system become slow, this is the very useful command to troubleshoot. If you have process which seems to hang and you want to stop the process, then you need pid of the process, so that you can terminate by using kill command.

Enter ps faux –cumulative to quickly list all running processes. Output will resemble the following:

USER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.1  1516  520 ?        Ss   May30   0:05 init [2]
root      1559  0.0  0.1  1564  536 ?        Ss   May30   0:00 /sbin/syslogd
root      1579  0.0  0.2  2512 1228 ?        S    May30   0:00 /bin/sh /usr/bin/
root      1598  0.0  0.1  2512  560 ?        S    May30   0:00  \_ /bin/sh /usr/
mysql     1599  0.0  3.2 97960 16464 ?       S    May30   0:02      \_ /usr/sbin
root      1600  0.0  0.0  1496  504 ?        S    May30   0:00      \_ logger -p
daemon    1673  0.0  0.0  1696  368 ?        Ss   May30   0:00 /usr/sbin/atd
root      1676  0.0  0.1  1776  748 ?        Ss   May30   0:02 /usr/sbin/cron
root      1683  0.0  0.8 10516 4216 ?        S    May30   0:00 /usr/sbin/apache
www-data  1696  0.0  0.3 10520 1988 ?        S    May30   0:00  \_ /usr/sbin/apa
www-data  1697  0.0  0.3 10520 1960 ?        S    May30   0:00  \_ /usr/sbin/apa
root     11830  0.0  0.1  3472  896 ?        Ss   May30   0:03 /usr/sbin/sshd
root     28133  0.0  0.3 14576 2000 ?        Ss   02:38   0:00  \_ sshd: root@pt
root     28166  0.0  0.2  2568 1412 pts/0    Rs   02:38   0:00      \_ -bash
root     13826  0.0  0.1  2500  816 pts/0    R+   03:49   0:00          \_ ps fa

Column Names

Commonly-used columns:

1. USER – Username – The name of the user associated with the process
2. PID – Process ID – The unique numeric identifier assigned to the process
3. %CPU – Percentage of CPU – Time used (total CPU time divided by length of time the process has been running)
4. %MEM – Percentage of RAM – Memory used (memory used divided by total memory available)
5. VSZ – Virtual Memory Size – Size of the process in virtual memory expressed in KiB
6. RSS – ???
7. TTY – Terminal controlling the process
8. STAT – Process State – Possible values:
* R – Running
* S – Sleeping (may be interrupted)
* D – Sleeping (may not be interrupted) – used to indicate process is handling input/output
* T – Stopped or being traced
* Z – Zombie or “hung” process
9. START – The date or time at which the process started
10. TIME – Cumulative CPU time used by the process and the child processes started by the process
11. COMMAND – Command used to start the process

Example:1

[root@localhost ~]# ps
  PID TTY          TIME CMD
 3371 pts/2    00:00:00 bash
 3476 pts/2    00:00:00 ps

Using process Option you can identify the process id, UID, PID, PPID, time and program.

Options
-e using this Option you find every process on the system.

Example 2:

[root@localhost ~]# ps -e | head
  PID TTY          TIME CMD
    1 ?        00:00:00 init
    2 ?        00:00:00 migration/0
    3 ?        00:00:00 ksoftirqd/0

-ef using this option you can get the information like owner of the process, process id, process parent id and name of the program.

Example : 3

[root@localhost ~]# ps -ef | head
UID        PID  PPID  C STIME TTY          TIME CMD

root         1     0  0 07:39 ?        00:00:00 init [5]
root         2     1  0 07:39 ?        00:00:00 [migration/0]
root         3     1  0 07:39 ?        00:00:00 [ksoftirqd/0]
root         4     1  0 07:39 ?        00:00:00 [watchdog/0]

u display user-oriented format and it’s easy to understand, which process is taking percentage of CPU, Mem, etc.

Example: 4

[root@localhost ~]# ps u
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      2375  0.0  0.0   1624   456 tty1     Ss+  07:40   0:00 /sbin/mingetty tty1
root      2378  0.0  0.0   1624   432 tty2     Ss+  07:40   0:00 /sbin/mingetty tty2
root      2379  0.0  0.0   1628   464 tty3     Ss+  07:40   0:00 /sbin/mingetty tty3
root      2380  0.0  0.0   1628   440 tty4     Ss+  07:40   0:00 /sbin/mingetty tty4
root      2381  0.0  0.0   1624   436 tty5     Ss+  07:40   0:00 /sbin/mingetty tty5
root      2392  0.0  0.0   1628   440 tty6     Ss+  07:40   0:00 /sbin/mingetty tty6
root      2679  0.0  0.1   4488  1380 pts/1    Ss+  07:43   0:00 bash
root      3371  0.0  0.1   4492  1392 pts/2    Ss   07:45   0:00 -bash
root      3659  0.0  0.0   4216   936 pts/2    R+   08:32   0:00 ps u

Tags: linux ps, ps linux command

Category: Linux Administration