linux

Synopsis

Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged in a Linux distribution.

Basic System Commands

Command	Description
`exit`	Close / exit from a from terminal
`xkill`	After right click on any window to close
`poweroff`	Turn off the system using terminal
`reboot`	Restart the system using terminal

File Commands

Command	Description
`ls`	List files in current directory
`ls -l`	List files in long format
`ls -a`	List all files including hidden files
`pwd`	Print working directory
`cd`	Change directory
`cd ..`	Change directory to parent directory
`cd ~`	Change directory to home directory
`cd -`	Change directory to previous directory
`mkdir`	Create directory
`mkdir -p`	Create directory and parent directories
`touch`	Create file
`cp`	Copy file
`cp -r`	Copy directory
`mv`	Move file
`mv -r`	Move directory
`rm`	Remove file
`rm -r`	Remove directory
`rm -f`	Force remove file
`rm -rf`	Force remove directory

File Permissions

Command	Description
`chmod`	Change file permissions
`chmod 777`	Change file permissions to 777
`chmod u+x`	Change file permissions to executable for user
`chmod g+x`	Change file permissions to executable for group

Privilege Escalation

Command	Description
`sudo -l`	List sudo permissions
`sudo -u`	Run command as another user
`sudo -i`	Run shell as another user
`sudo !!`	Run previous command as root
`su`	Run shell as another user

SSH

Command	Description
`ssh user@host`	Connect to remote host
`ssh -p port user@host`	Connect to remote host on specific port
`ssh-copy-id`	Copy SSH key to remote host
`ssh-keygen`	Generate SSH key

System Info

Command	Description
`uname`	Print system information
`uname -a`	Print all system information
`uname -r`	Print kernel release
`uname -m`	Print machine hardware name
`hostname`	Print system hostname
`hostname -I`	Print all IP addresses
`hostname -i`	Print IP address
`date`	Print system date and time
`cal`	Print calendar
`uptime`	Print system uptime
`whoami`	Print current user
`w`	Print who is logged in
`finger`	Print information about user
`id`	Print effective user and group id
`groups`	Print all groups current user is in
`last`	Print last logged in users
`lastlog`	Print when users last logged in
`free`	Print free and used memory
`df`	Print disk usage
`du`	Print file space usage
`du -h`	Print file space usage in human readable format
`man`	Print manual page (exit with q)
`top`	Get all running procsee & hardware consumptions

Shortcuts

Command	Description
`Ctrl + a`	Go to the beginning of the line you are currently typing on
`Ctrl + e`	Go to the end of the line you are currently typing on
`Ctrl + u`	Clear the line before the cursor position. If you are at the end of the line, clears the entire line.
`Ctrl + k`	Clear the line after the cursor position. If you are at the beginning of the line, clears the entire line.
`Ctrl + w`	Delete the word before the cursor.
`Ctrl + r`	Let you search through previously used commands.
`Ctrl + l`	Clears the Screen, similar to the clear command.
`Ctrl + c`	Kill whatever you are running.
`Ctrl + d`	Exit the current shell.
`Ctrl + z`	Puts whatever you are running into a suspended background process. fg restores it.
`Ctrl + s`	Stop output to the screen (for long running command).
`Ctrl + q`	Allow output to the screen (for long running command).
`Ctrl + x`	Use the arrow keys to navigate through the command line history.
`Ctrl + _`	Undo.
`Ctrl + Alt + T`	Open terminal using keyboard
`Ctrl + Shift + N`	Open new terminal window
`Ctrl + Shift + T`	Open new tab in terminal
`Ctrl + Shift + C`	Copy selected text from terminal
`Ctrl + Shift + V`	Paste any coppied text in terminal

// Also press up & down arrow respectively to get the former & latter executed commands in a terminal .

Text Editors

Command	Description
`nano`	Nano is a simple text editor for Unix-like computer operating systems.
`vim file`	Vim is a highly configurable text editor built to enable efficient text editing.
`vi file`	Vi is a screen-oriented text editor originally created for the Unix operating system.
`emacs file`	Emacs is a family of text editors that are characterized by their extensibility.

Command	Description
`tar -xvf file.tar`	Extract tar file
`tar -cvf file.tar directory`	Create tar file
`tar -tvf file.tar`	List contents of tar file
`tar -xvzf file.tar.gz`	Extract tar.gz file
`tar -cvzf file.tar.gz directory`	Create tar.gz file
`tar -tvzf file.tar.gz`	List contents of tar.gz file
`tar -xvjf file.tar.bz2`	Extract tar.bz2 file
`tar -cvjf file.tar.bz2 directory`	Create tar.bz2 file
`tar -tvjf file.tar.bz2`	List contents of tar.bz2 file
`unzip file.zip`	Extract zip file
`zip file.zip directory`	Create zip file
`zip -r file.zip directory`	Create zip file recursively
`unrar x file.rar`	Extract rar file
`rar a file.rar directory`	Create rar file

Disk Usage

Command	Description
`df`	Show disk usage
`du`	Show file space usage
`du -h`	Show file space usage in human readable format
`du -a`	Show file space usage for all files
`du -s`	Show summarized file space usage
`du -sh`	Show summarized file space usage in human readable format
`du -c`	Show summarized file space usage with grand total
`fdisk -l`	Show all disk partitions
`fdisk /dev/sda`	Show disk partitions for /dev/sda
`mount`	Show mounted filesystems

Search

Command	Description
`grep pattern file`	Search for pattern in file
`grep -r pattern directory`	Recursively search for pattern in directory
`grep -v pattern file`	Invert match, print non-matching lines
`grep -l pattern file`	Print only filenames with matches
`grep -i pattern file`	Ignore case distinctions
`grep -r -i pattern directory`	Recursively search for pattern in directory, ignoring case
`locate file`	Find file
`find / -name file`	Find file in /
`find / -name file -type f`	Find only files in /

Networking

Command	Description
`ifconfig`	Configure a network interface
`ifconfig -a`	Configure all network interfaces
`ifconfig eth0`	Configure eth0 network interface
`iwconfig`	Get information for WiFi adapters
`nmcli networking off`	Turn off network connections
`nmcli networking on`	Turn on network connections
`systemctl stop NetworkManager`	Turn off network connections
`systemctl start NetworkManager`	Turn on network connections
`systemctl restart NetworkManager`	Restart network connectionss
`whois domain`	Get whois information for domain
`dig domain`	Get DNS information for domain
`dig -x host`	Get DNS information for host
`host domain`	Get DNS information for domain
`host -t mx domain`	Get MX records for domain
`hostname -I`	Get all IP addresses
`hostname -i`	Get IP address

VIM

Command	Description
`h`	move cursor left
`j`	move cursor down
`k`	move cursor up
`l`	move cursor right
`gg`	go to the first line of the document
`G`	go to the last line of the document
`zz`	center cursor on screen
`0`	jump to the start of the line

Emacs

Command	Description
`CTRL+O`	Write the current file to disk
`CTRL+X`	Close the current file buffer / Exit from Nano
`CTRL+R`	Insert another file into the current one
`ALT+<`	Switch to the previous file buffer
`ALT+>`	Switch to the next file buffer
`ALT+D`	Count the number of words, lines, and characters
`CTRL+L`	Refresh (redraw) the current screen

Tree

Command	Description
`tree`	It will display the contents of the working directory recursively showing sub-directories and files
`tree -a`	Display also the hidden files
`tree -f`	Display contents with the full path prefix
`tree -d`	Display only the subdirectories
`tree -df`	Display subdirectories with their paths
`tree -L 2`	Specifying depth of the directory
`tree -P init.py*`	Display only those files that match the pattern
`tree --du`	Reports the size of each element
`tree -J`	Outputs the directory tree as an JSON formatted array
`tree -o direc_tree.txt`	Redirect the tree’s output to filename