Linux Admin - Basic CentOS Linux Commands


Advertisements

Before learning the tools of a CentOS Linux Administrator, it is important to note the philosophy behind the Linux administration command line.

Linux was designed based on the Unix philosophy of “small, precise tools chained together simplifying larger tasks”. Linux, at its root, does not have large single-purpose applications for one specific use a lot of the time. Instead, there are hundreds of basic utilities that when combined offer great power to accomplish big tasks with efficiency.

Examples of the Linux Philosophy

For example, if an administrator wants a listing of all the current users on a system, the following chained commands can be used to get a list of all system users. On execution of the command, the users are on the system are listed in an alphabetical order.

[root@centosLocal centos]# cut /etc/passwd -d":" -f1 | sort 
abrt 
adm 
avahi 
bin 
centos 
chrony 
colord 
daemon 
dbus

It is easy to export this list into a text file using the following command.

[root@localhost /]# cut /etc/passwd -d ":" -f1 > system_users.txt        
[root@localhost /]# cat ./system_users.txt | sort | wc –l 
40       
[root@localhost /]#

It is also possible to compare the user list with an export at a later date.

[root@centosLocal centos]#  cut /etc/passwd -d ":" -f1 > system_users002.txt && 
   cat system_users002.txt | sort | wc -l 
41 
[root@centosLocal centos]# diff ./system_users.txt ./system_users002.txt  
evilBackdoor [root@centosLocal centos]#

A new user, “evilBackdoor", has been added to the system.

With this approach of small tools chained to accomplish bigger tasks, it is simpler to make a script performing these commands, than automatically email results at regular time intervals.

Basic Commands every Linux Administrator should be proficient in are −

In the Linux world, Administrators use filtering commands every day to parse logs, filter command output, and perform actions with interactive shell scripts. As mentioned, the power of these commands come in their ability to modify one another through a process called piping.

The following command shows how many words begin with the letter a from the CentOS main user dictionary.

[root@centosLocal ~]# egrep '^a.*$' /usr/share/dict/words | wc -l 
25192 
[root@centosLocal ~]#

Useful Video Courses


Video

Linux Shell Scripting Online Training

57 Lectures 7.5 hours

Mamta Tripathi

Video

Mac Linux Command Line for Beginners

25 Lectures 3 hours

Lets Kode It

Video

Setup Own VPN Server with Android, iOS, Win & Linux Clients

14 Lectures 1.5 hours

Abhilash Nelson

Video

Bash Scripting, Linux and Shell Programming

58 Lectures 2.5 hours

Frahaan Hussain

Video

Fundamentals of Unix and Linux System Administration

129 Lectures 23 hours

Eduonix Learning Solutions

Video

RedHat Linux: Essentials

23 Lectures 5 hours

Pranjal Srivastava, Harshit Srivastava

Advertisements