How to use shell commands for daily administration tasks

List Directory Contents with permissions

[ahmed@Linux ~] $ ll
[ahmed@Linux ~] $ ls –al

List Directory contents with their estimated space usage in human readable format

[ahmed@Linux ~] $ du -ach --mac-depth=1 /home/oracle

Clear Shell Screen

[ahmed@Linux ~] $ clear

Top memory process

[ahmed@Linux ~] $ top
(Press shift + m by sorting memory descending)

Check who is in shell

[ahmed@Linux ~] $ who
[ahmed@Linux ~] $ w

Force logout user

[ahmed@Linux ~] $ pkill –KILL –u ahmed

Kill process which user is using

[ahmed@Linux ~] $ w
[ahmed@Linux ~] $ ps  –u  ahmed
[ahmed@Linux ~] $ kill -9 3922
(where 3922 is PID of soffice process)

Check all services

[ahmed@Linux ~] $  sudo   /sbin/service   --status-all

Check individual service

[ahmed@Linux ~] $ sudo  /sbin/service  httpd  status
[ahmed@Linux ~] $ sudo  /sbin service  mysqld status

Check logs

[ahmed@Linux ~] $ sudo  tail  /var/log/messages
[ahmed@Linux ~] $ sudo  tail  /var/log/secure
[ahmed@Linux ~] $ sudo  tail  /var/log/httpd/error_log

Check quota

[ahmed@Linux ~] $sudo  tail  /usr/sbin/repquota –a

Netstat

[ahmed@Linux ~] $netstat -tunlp (lists the ports and which program & PID has it open)
-t  = tcp
-u = udp
-n = display port numbers not names
-l  = only listening programs (ie:  servers)
-p = display PID/program name

List open files

[ahmed@Linux ~] $lsof  -i
[ahmed@Linux ~] $ lsof  -p  ProcessID

Check Process

[ahmed@Linux ~] $ pstree
[ahmed@Linux ~] $ ps aux
[ahmed@Linux ~] $ ps aux | grep daemon

• To show all processes running on your system, at prompt, type the following

[ahmed@Linux ~] $ ps –ef
[ahmed@Linux ~] $ ps –ef | pg
[ahmed@Linux ~] $ ps gv

• Table Description

USER             User login name
PID              Process ID
PPID             Parent Process ID
C                CPU utilization of process
STIME            Start time of process
TTY              Controlling workstation for the process
TIME             Total execution time for the process
CMD              Command

Kill Process

[ahmed@Linux ~] $sudo kill  -9 ProcessID

Check which IP is being blocked by tcpwrapper

[ahmed@Linux ~] $ cat  /etc/hosts.deny
[ahmed@Linux ~] $ sudo  vi /etc/hosts.deny  (removing blocked ip)
[ahmed@Linux ~] $ sudo  vi /etc/hosts.allow  (adding trusted  ip)

Check manual of program

[ahmed@Linux ~] $man man
[ahmed@Linux ~] $ man sendmail

Locating another command or program

[ahmed@Linux ~] $ whereis  Mail
[ahmed@Linux ~] $ whatis  ls
[ahmed@Linux ~] $ updatedb
[ahmed@Linux ~] $ locate vi
(Note: updated is system database update for locate command.
You should run this frequently or add as daily cron job).
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