Linux Basic Guide (Ubuntu/Kali)

Installing WSL

dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart

After restart:

wsl --install

After restart, go to Microsoft Store, pick whatever distribution you like & install it.

Working Directory (WD)

• To check the working directory use pwd

cd (Change Directory)

Usage: cd {PATH}

• To get to parent folder use cd ..
• To get to grandparent folder use cd ../..
• To get to root cd /
• To get to home cd ~
• To get to a child directory cd ./child/childofchild

Root Permissions

• Append sudo before any command to run as root
• To login as root use sudo su -

Files/Directories

• Creating file: touch file.txt
• Creating directory: mkdir dir
• Moving file: mv file.txt /path/to/anothername.txt
• Renaming file: mv file.txt another.txt
• Removing file: rm file.txt
• Removing Directory: rm -d
• Listing all contents of WD: ls
• Listing all contents of WD with extra details: ll
• Copying a file: cp old_code.cpp new_code.cpp

Working with files

• To output the file cat file.txt
• To edit the file sudo nano file.txt

Running executables

• Running a local executable ./app
• Running a global executable app
• Running a global executable that matchs some command \app

Package Manager

• Installing: sudo apt install {package}
• Updating: sudo apt update
• Upgrading sudo apt upgrade
• Removing sudo apt remove {package}

Helping Programs

• timeout {SECONDS} {COMMAND} - Exits with error code 127 in case it exceeds time
• time {COMMAND} - Measures execution time of a command
• cron - Schedule programs & scripts, for using crontab -e
• curl - Client for sending web requests
• man {PROGRAM_NAME} - Tells you how to use the program/command
• which {PROGRAM_NAME} - Shows you the path of the program

Environment Variables

The system has some variables with assigned values, so programs can use it

• Checking environment variables: env
• Writing an environment variable in current session: export VAR="value"
• Writing a permanent environment variable: echo 'export VAR="value"' >> ~/.bashrc
• Outputting an environment variable: echo $VAR
• Outputting last exit code: echo $?

File Permissions

When doing ll, here is an expected output:

drwxrwxrwx root root
lrwxr-xr-- root root
-rw-rw-r-- user user

• First character: file type d=directory, l=link, -=file

• Next 3 characters: Permissions of owner

• Next 3 characters: Permissions of group

• Next 3 characters: Permissions of others

• Permissions rwx means read, write, execute.

• After it the owner

• After it the group

• Changing owner: chown

• Changing group: chgrp

• Changing permissions: chmod

For more, check this page

Tricks

• You can do multiple commands in same line:
  • mkdir child; cd child - Using ; it will run these two commands
  • mkdir child && cd child- Using && it will run the second command if the first have a zero exit code
  • ./code | ./checker - Using | it will run first command and redirect its output to second command input