Linux Cheat Sheet every DevOps Novice must have

What is Linux ?

Linux is the most important operating system in Networking World. Many Network Engineers, Network Administrators and Network Technicians use Linux in different areas of Computer Networking. They use different commands of Linux everyday. But sometimes, some commands can be forgotten. To overcome this issue, I have created a Linux Cheat Sheet for you! In this page, you will find Linux Cheat Sheet Commands.

Is Linux an Operating System?

Because of the fact that there are many versions, “is Linux a Opearing Sytem?” quesiton is very common. The answer is certainly Yes! Linux is an Open source Unix ilke Operating System. It is based on Linux Kernel. This Linux kernel was firstly released by Linus Torvalds at 17 September 1991. There are different distributions of Linux, some of these are:

• Red Hat
• Ubuntu
• Fedora
• Debian
• Suse etc.

All these Linux versions uses the same Linux commands and all the Basic Linux commands are similar in these Operating Systems. Linux find command, Linux delete command, Linux add user, Linuc copy file, Linux password change, Linux unzip etc. All these commands are similar in these versions. So, you can use Linux Cheat Sheet Commands on all these Linux distributions. In other words, you can benefit Linux command line cheat sheet on Red Hat, Ubuntu, Fedora, Debian, Suse etc.

I have realised that people often tend to forget that the Linux is not about the GUI its all about how much you can operate via the Terminal. So what I have tried here is tried to inculcate all the commands in some group in the form of list.

For the basic linux commands. You can have a look at these articles; In which I have included most of the basic commands.

Part 1 - Fundamental Linux Commands

Part 2 - Fundamental Linux Commands

Types of Commands are as follows:

File Commands

ls -l    lists files detailly (file type, user, permission etc)
ls -lh    lists files detailly with human readable format
ls -al    lists files detailly with hidden files
pwd    shows present directory
mkdir directory    creates a directory
rm xyz    deletes file xyz
rm -r /xyz    deletes directory /xyz and its contents recursively
rm -f abc    forcefully deletes abc file without confirmation
rm -rf /xyz    forcefully deletes directory /xyz recursively
cp aaa bbb    copies aaa file to bbb file
cp -r /xxx /yyy    copies /xxx directıry to /yyy directory
mv aaa bbb    renames or moves file aaa to file bbb
touch abc    creates an empty file named abc
cat abc    used to view file abc
less abc    browse through a text file abc
head abc    displays first 10 lines of file abc
tail abc    displays last 10 lines of file abc
tail -f abc    displays last 10 lines of file abc and follow it as it grows
tail -F abc    outputs last lines of abc as it changes
file abc    gets type of abc
gpg -c abc    encrypts file abc
gpg abc    decrypts file abc
gpg abc    decrypts file abc
gpg abc    decrypts file abc
dir    shows files in the current directory
put abc    uploads file ‘abc’ from local to remote device
get file    downloads file ‘abc’ from remote to local device

ls options which are included

-a display hidden files 
-R recursive List gets visible
-r reverse order gets visible
-t sort by last modified
-m comma-separated output

Install Commands

Considering we are operating on Red Hat Enterprise Linux

yum search keyword    compresses abc file using gzip.
yum install abc    installs abc package
yum info abc    displays description and summary info about abc package
rpm -i abc.rpm    installs package from local file named abc.rpm
yum remove abc    Remove/uninstall abc package
yum list installedl    lists all installed packages with yum
yum search [keyword]    finds a package by a related keyword
yum info [package_name]    shows package information and summary
yum install [package_name.rpm]    installs a package using the YUM package manager
dnf install [package_name.rpm]    installs a package using the DNF package manager
apt-get install [package_name]    installs a package using the APT package manager
rpm -i  [package_name.rpm]    installs an .rpm package from a local file
rpm -e [package_name.rpm]    removes an .rpm package

Disk Usage Commands

df    shows file system disk usage
du    shows disk usage for specific directories
du -a    shows disk usage for all the files
du -s    shows used total disk space
free    shows free and used memory on the system
fdisk    used to manipulate disk partition table
fdisk -l    used to list disc partition table
sfdisk    used to manipulate disk partition table with more features
cfdisk    linux partition editor with an interactive user interface
findmnt    lists all mounted file systems
mount     mounts a filesystem
parted    lists and modifies partitions
parted -l    lists the partition details
lsblk    lists all the storage blocks including partitions
blkid    prints the block device partitions and storage media

File Permissions

chown user    changes ownership of a file/directory
chown user:group filename    changes user and group for a file or directory
File Permissions
r (read) permission, 4
w (write) permission, 2
x (execute) permission, 1
-= no permission

File Owner    owner/group/everyone

File Permissions Examples    777 | Owner, Group, Everyone has rwx permissions

744 | Owner has rwx permission, Group, Everyone has r permission

755 | Owner has rwx permission, Group, Everyone has rx permissions

776 | Owner, Group has rwx permission, Everyone has rw permissions

User Information Commands

id    shows user&group ids of the current user
last    shows the last users logged on
whoami    shows who you are logged in as
who    shows who is logged into the system
w    shows who is logged in and what they do
groupadd test    creates group “test”
useradd -c “GK” -m Gokhan    creates “Gokhan” account with comment “GK”
userdel Gokhan    deletes account “Gokhan”
usermod -aG Networkers Gokhan    adds account “Gokhan” to the “Networkers” group

System Information Commands

uname -a    shows Linux system info
uname -r    shows kernel release info
cat /etc/redhat-release    shows installed redhat version
uptime    displays system running/life time
hostname    shows system host name
hostname -I    shows ip addresses of the host
last reboot    displays system reboot history
date    displays current date and time
cal    displays monthly calendar
mount    shows mounted filesy­stems

Help Commands

command -h / command –help    to review all available options of the “command”
info command    to find info documents about the “command”
whatis command    displays a single line description about the”command”
$ man UNIXCOMMAND    to view detailed man page of the “command”
apropos    used to search man pages for available commands on a specific functionality.

I hope this gives you a gist regarding the Linux Commands and helps to become a Linux Master. Eventual practice of commands helps you to retain the knowledge of commands used so please feel free to use the commands rather than interacting with the GUI. It will definitely help you to make you a good hold of Linux Commands.