Introduction
Linux is a powerful and versatile operating system widely used in software development, system administration, and DevOps. Mastering Linux commands is essential for navigating the file system, managing processes, and automating tasks efficiently. This guide covers the most common Linux commands that every software engineer should know, providing a solid foundation for working effectively in a Linux environment. Let's dive into the key Linux commands you should be familiar with.
Basic Commands
1. ls
Purpose: List directory contents.
Example: ls -l (detailed list)
2. cd
Purpose: Change directory.
Example: cd /home/user (navigate to user's home directory)
3. pwd
Purpose: Print working directory.
Example: pwd
4. mkdir
Purpose: Create a new directory.
Example: mkdir new_directory
5. rmdir
Purpose: Remove an empty directory.
Example: rmdir old_directory
6. rm
Purpose: Remove files or directories.
Example: rm file.txt (remove a file), rm -r directory (remove a directory and its contents)
7. cp
Purpose: Copy files or directories.
Example: cp source.txt destination.txt (copy file), cp -r source_dir destination_dir (copy directory)
8. mv
Purpose: Move or rename files or directories.
Example: mv oldname.txt newname.txt (rename file), mv file.txt /new/path/ (move file)
9. touch
Purpose: Create an empty file or update the timestamp of an existing file.
Example: touch newfile.txt
10. cat
Purpose: Concatenate and display file content.
Example: cat file.txt
11. more
Purpose: View file content one screen at a time.
Example: more file.txt
12. less
Purpose: View file content with backward movement.
Example: less file.txt
13. head
Purpose: Output the first part of a file.
Example: head -n 10 file.txt (first 10 lines)
14. tail
Purpose: Output the last part of a file.
Example: tail -n 10 file.txt (last 10 lines) File Permissions
15. chmod
Purpose: Change file permissions.
Example: chmod 755 script.sh
16. chown
Purpose: Change file owner and group.
Example: chown user:group file.txt
17. chgrp
Purpose: Change group ownership.
Example: chgrp group file.txt
18. uname
Purpose: Print system information.
Example: uname -a
19. df
Purpose: Report file system disk space usage.
Example: df -h (human-readable format)
20. du
Purpose: Estimate file space usage.
Example: du -sh directory (summary of directory)
21. top
Purpose: Display task manager.
Example: top
22. htop
Purpose: Interactive process viewer.
Example: htop
23. ps
Purpose: Report a snapshot of current processes.
Example: ps aux
24. free
Purpose: Display memory usage.
Example: free -h
25. uptime
Purpose: Show how long the system has been running.
Example: uptime
26. ping
Purpose: Check network connectivity.
Example: ping google.com
27. ifconfig
Purpose: Configure network interfaces.
Example: ifconfig
28. ip
Purpose: Show/manipulate routing, devices, policy routing, and tunnels.
Example: ip addr
29. netstat
Purpose: Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
Example: netstat -tuln
30. ss
Purpose: Another utility to investigate sockets.
Example: ss -tuln
31. scp
Purpose: Secure copy (remote file copy program).
Example: scp file.txt user@remote:/path/
32. rsync
Purpose: Remote file and directory synchronization.
Example: rsync -avz source/ user@remote:/path/
33. grep
Purpose: Print lines matching a pattern.
Example: grep "search_term" file.txt
34. awk
Purpose: Pattern scanning and processing language.
Example: awk '{print $1}' file.txt
35. sed
Purpose: Stream editor for filtering and transforming text.
Example: sed 's/old/new/g' file.txt
36. apt-get (Debian/Ubuntu)
Purpose: Handle packages.
Example: sudo apt-get update (update package index), sudo apt-get install package_name (install a package)
37. yum (RHEL/CentOS)
Purpose: Package manager for RPM-based distributions.
Example: sudo yum install package_name
*38. dnf (Fedora) *
Purpose: Modernized version of yum.
Example: sudo dnf install package_name
39. pacman (Arch)
Purpose: Package manager for Arch Linux.
Example: sudo pacman -S package_name Archiving and Compression
40. tar
Purpose: Archive files.
Example: tar -czvf archive.tar.gz directory/
41. zip
Purpose: Package and compress files.
Example: zip -r archive.zip directory/
42. unzip
Purpose: Extract compressed files.
Example: unzip archive.zip
43. gzip
Purpose: Compress files.
Example: gzip file.txt
44. gunzip
Purpose: Decompress files.
Example: gunzip file.txt.gz
45. fdisk
Purpose: Partition table manipulator.
Example: sudo fdisk /dev/sda
46. mkfs
Purpose: Build a Linux file system.
Example: sudo mkfs.ext4 /dev/sda1
47. mount
Purpose: Mount a file system.
Example: sudo mount /dev/sda1 /mnt
48. umount
Purpose: Unmount a file system.
Example: sudo umount /mnt
49. adduser
Purpose: Add a user to the system.
Example: sudo adduser username
50. usermod
Purpose: Modify a user account.
Example: sudo usermod -aG groupname username
51. passwd
Purpose: Change user password.
Example: passwd username
52. whoami
Purpose: Print the current user id and name.
Example: whoami
53. groups
Purpose: Show user groups.
Example: groups username
54. kill
Purpose: Terminate a process.
Example: kill PID
55. killall
Purpose: Terminate all processes by name.
Example: killall process_name
56. pkill
Purpose: Send a signal to a process by name.
Example: pkill process_name
57. bg
Purpose: Resume a job in the background.
Example: bg %1
58. fg
Purpose: Bring a job to the foreground.
Example: fg %1
59. export
Purpose: Set environment variables.
Example: export VAR=value
60. alias
Purpose: Create an alias for a command.
Example: alias ll='ls -la'
61. source
Purpose: Execute commands from a file in the current shell.
Example: source ~/.bashrc
62. history
Purpose: Show command history.
Example: history
63. clear
Purpose: Clear the terminal screen.
Example: clear
64. exit
Purpose: Exit the shell.
Example: exit
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