- Linux Admin Tutorial
- CentOS Overview
- Basic CentOS Linux Commands
- File / Folder Management
- User Management
- Quota Management
- Systemd Services Start and Stop
- Resource Mgmt with systemctl
- Resource Mgmt with crgoups
- Process Management
- Firewall Setup
- Configure PHP in CentOS Linux
- Set Up Python with CentOS Linux
- Configure Ruby on CentOS Linux
- Set Up Perl for CentOS Linux
- Install and Configure Open LDAP
- Create SSL Certificates
- Install Apache Web Server CentOS 7
- MySQL Setup On CentOS 7
- Set Up Postfix MTA and IMAP/POP3
- Install Anonymous FTP
- Remote Management
- Traffic Monitoring in CentOS
- Log Management
- Backup and Recovery
- System Updates
- Shell Scripting
- Package Management
- Volume Management
- Linux Admin Useful Resources
- Linux Admin - Quick Guide
- Linux Admin - Useful Resources
- Linux Admin - Discussion
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Linux Admin - Basic CentOS Linux Commands
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 ~]#