CentOS command Cheat Sheet

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If you're new to CentOS, mastering the commands and tools will go a long way toward enhancing your productivity. The blog is a compilation of nearly every important CentOS command that you need to work smoothly. But before jumping on that, let's brush up with the basics.

A Quick Overview of CentOS

Community Enterprise Operating System or CentOS is a free and open-source commercial operating system compatible with Red Hat Enterprise Linux (RHEL). Gregory Kurtzer founded centOS, and CentOS developers use the RHEL source code to create a product that is quite similar to RHEL.

CentOS is a development platform that is one of the best and most influential Linux distributions available. It's a community-driven free software project that aims to create a stable foundation for open source communities. It's versatile, as well as safe and durable. It also includes multiple corporate-level security updates, making it a fantastic solution for any application. Have a look at the benefits of using CentOS:

It virtualises using a Kernel-based Virtual Machine and gives maximum availability and performance.
CentOS has a committed developer community that keeps it up to date and guarantees compatibility with both new and old applications.
CentOS releases are revised on average every six months, and each release has a ten-year support period.
Red Hat's security team is adept at detecting threats and maintaining a high level of security. The Security-Enhanced Linux kernel addition is also included with CentOS.

CentOS Commands Cheatsheet

Help Commands

whatis	It is used to find concise descriptions of system commands by searching the Whatis database for entire words.
which	Displays full path to shell commands
whereis	Search and discover command's binary, source, and man pages
apropos	Look for help and man pages containing specific phrases and instructions by searching a database of short descriptions.
man	Lists Manual pages for the respective command

File Operations

cat	Concatenate files or print a file on the monitor.
touch	Make a new file and modify the timestamps.
cp	Copy files or directories.
mv	Moves files or directories.
rm	Removes directories or files in a recursive manner
ln	It is used for creating a symbolic or hard link for a file.
less	Viewing a single file on a single page, along with the ability to go backwards.
head	Printing the first ten lines of a file.
tail	Printing the last ten lines of a file.
wc	Counts the total number of words or characters there are in a file.
stat	Shows the status of a file or a file system.
cut	Remove parts of input lines.
paste	Combine multiple lines of text in a single file.

Process Management

ps	Provide an update on existing procedures.
pstree	Displays a tree of processes.
top	Demonstrate real-time procedures.
kill	PID is used to terminate a process.
killall	Stop a process permanently via name
pkill	Looking up for processes or signals based on the same and other attributes.
pgrep	Look for information on the process.
ctrl+z	Stop the task instead of keeping it on halt permanently.
&	The addition of this after a command puts the process in the background.
jobs	Displays all the jobs running in process

Partitions and Disk Management

df	Report on the amount of disc space used by the file system.
mount	Mount a file system or see what's mounted.
unmount	Unmounts a file system
fuser	Identifies processes via files or sockets.
isof	Displays a list of the system's open files

Accounts and Security Administration

groupadd	Used for creating new groups
groupdel	Used for creating groups
groupmod	Manipulating the description of a particular group
useradd	Creating new users
userdel	Deleting new users
usermod	Modifying a user’s account
passwd	Updating a user’s password
vipw	Editing the password or shadow password of a group
vigr	Editing groups or shadow groups
chage	Modifying password policies

Networking

ifconfig	Set up the network interface.
route	Shows and manipulates IP routing table
ip	Replaces ifconfig, arp, and route by displaying and manipulating routing, devices, policies, and tunnels.
ifup	It brings up the network interfaces
ifdown	It brings the network interfaces down
ping	Sends ICMP ECHO_REQUEST to network hosts

Directory Operations

clear	Removes all the contents from your screen
pwd	Displays running directory on the screen
cd	Modifies directories
ls	Lists down all the content of a directory
mkdir	Creates a new directory
rmdir	Deletes null directories

Some Frequently-used CentOS Commands

top

This command provides a list of processes or threads that the system kernel is currently using. This is important for determining if something is clogging up your system's resources. The first section you'll notice is a summary, followed by the fields and columns heading, and finally, the task area. You'd use this to see if a process is hung or using up all of your system's resources before keeping it on halt.

Nmap

Nmap allows you to swiftly scan networks for open ports, application version information, and a variety of other important and sensitive data. You can close any gaps in your security plan by listing information such as what ports are open. Nmap is a powerful tool, and reading the man pages is a must to comprehend all of the choices and capabilities available fully.

rpm -ql <packagename> or dpkg -L <packagename>

These two commands are used to quickly locate all of the files connected with a specific package. It will display all of the files as well as the package name's location. Rpm is for RHEL/CentOS systems, while dpkg is for Debian systems.

sosreport

Sosreport is one of the scripts that our customers regularly use during break/fix issues. It creates a backup of the system's configuration and diagnostic data, which can be utilised for further debugging and troubleshooting. It's compatible with xsos, a software that reads the reports created by sosreport.

lsmod

This command organises and arranges the output of modules in /proc/modules as well as any presently loaded kernel modules.

Final Thoughts

Finally, CentOS comes with a plethora of other tools and utilities, and the ones mentioned earlier cover pretty much all the crucial and frequently-used ones.

Category: Tutorials Linux