Basic Linux Commands

Introduction to Linux

• Linux is an open-source operating system kernel.It is suitable for diverse environments.

• It has a powerful command-line interface (CLI) alongside user-friendly graphical interfaces.

• Multiuser and Multitasking: It supports multiple users and tasks running concurrently. This makes it suitable for servers, where many users might need access, and for desktops, which require multitasking capabilities.

• Security: Linux's open-source nature facilitates security audits and timely updates.

• Variety of Distributions: Some popular ones include Ubuntu, Fedora, Debian, CentOS, and Arch Linux.

• Package Management: Linux distributions use package management systems (e.g., APT, YUM, and Pacman) to facilitate the installation, removal, and updating of software.

• Linux is a popular choice for servers, embedded systems, and personal computers.

• Linux has GPL :General Public License

• It focuses on shell scripting,networking, terminal,programming.

• It is secure.

• Updates are less than window

Some linux basic commands

File and Directory Management

**ls (list) :**List all contents (files and directories) in the current directory.

1. • ls-h: Human-readable file sizes.

     • ls -a: List all files and directories, including hidden ones.

     • ls -l: List files and directories in detailed format.

     • ls -t: List files and directories sorted by modification time.

     • ls -rt: List files and directories in reverse order of their names

2. pwd (print working directory) : Print the name of the directory that the user is currently working in.

3. **cd(change directory):**allows the user to change to a specified directory.

4. mkdir(make directory): allows the user to create a new directory..

   • Usage: mkdir directory_name

   • Along with mkdir we can use the "-p" flag which will create sub-directories (directories within a directory) if it does not exist.

5. touch :Create an empty file.

   • Usage: touch file_name

6. cp :Copy files or directories.

   • Usage: cp source_file destination_directory

   • cp -r: Copy directories recursively.

7. mv :Move or rename files or directories.

   • Usage:mv source_file destination

8. rm (remove): Remove files or directories.

   • Usage: rm file_name

   • rm -r: Remove directories recursively.

With this command, we can use the "-r" flag, which removes the files recursively within a directory but do not use "-rf" which will forcefully delete the files and will not give a prompt when deleting important files.

File viewing and Editing

1. cat(concatenate): Display the contents of a file.

   • Usage: cat file_name

2. more and less Display file contents one screen at a time.

   • Usage: more file_name & less file_name

3. head and tail Display the beginning or end of a file.

   • Usage: head file_name & tail file_name

4. grep Search for text in files using patterns.

   • Usage: grep "pattern" file_name

File permission and ownership

1. chmod :Change file permissions.

   • Usage: chmod permissions file_name

   • ls -l : to see permission of file or dir

2. chown command : change ownership

Process Management

1. ps : List running processes.

2. kill: Terminate processes.

   • Usage: kill PID

3. top: Display active processes in real-time

• man :Access the manual pages for commands.

  • Usage: man command_name

System Information

• df: Display disk space usage

• du: Display file and directory space usage

• lscpu :Display CPU

Compress and archieve

• tar: Archive and compress files.

  • Usage: tar options archive_name files/directories

    • -c: Create a new archive.

    • -z: Compress the archive using gzip.

• wget : Download files from the internet.

  • Usage: wget URL

Network Commands:

• ping: Check network connectivity to a specific host.

• ifconfig or ip: Display network interface information.

Administrative Tasks

whoami:displays the username of the current user when this command is entered.

Sudo:execute commands with administrative privileges

grep <search_word> <filename> //searches for word in a file
   -i overlook case sensitivity

   -R looks through dir as well.

   -v reverse search, searches everything except given search word

sed /s/<search-word>/<reaplce_word>/g //sed allows editing of file without opening it
        /s search

        /g global

less <filename> // reads  file without allowing to edit. (readonly)