Linux basic commands for managing the system

Linux provides a rich set of commands for managing the system, files, networking, processes, and much more. Below are some of the commonly used Linux commands and their explanations:

File and Directory Management

1. ls – List directory contents.

ls

ls -l     # Long format

ls -a     # Show hidden files

ls -lh    # Long format with human-readable file sizes

2. cd – Change directory.

cd /path/to/directory

cd ..     # Move to parent directory

cd ~      # Move to home directory

3. pwd – Print the current working directory.

pwd

4. mkdir – Create a new directory.

mkdir new_directory

5. rmdir – Remove an empty directory.

rmdir directory_name

6. rm – Remove files or directories.

rm file_name

rm -r directory_name  # To remove non-empty directory

rm -rf directory_name  # Force remove without confirmation

7. cp – Copy files or directories.

cp source_file destination_file

cp -r source_dir destination_dir  # Copy a directory

8. mv – Move or rename files and directories.

mv old_name new_name

mv file_name /path/to/destination/

9. find – Search for files in a directory hierarchy.

find /path/to/directory -name "filename"

find / -type f -name "*.txt"  # Search for .txt files

File Permissions

10. chmod – Change file permissions.

chmod 755 file_name  # Read, write, execute for owner; read, execute

for group and others

chmod u+x file_name  # Add execute permission for user

11. chown – Change file ownership.

chown user:group file_name

 

chown -R user:group directory_name  # Change ownership recursively

12. chgrp – Change group ownership of a file or directory.

chgrp group_name file_name

Process Management

13. ps – Display information about running processes.

ps aux  # Show all running processes

ps -ef  # Full-format listing

14. top – Display dynamic real-time system information (e.g., CPU, memory usage).

top

15. htop – Interactive process viewer (enhanced version of top).

htop

16. kill – Terminate a process.

kill <PID>  # Terminate process by PID

kill -9 <PID>  # Force kill a process

17. killall – Kill processes by name.

killall process_name

18. bg – Resume a job in the background.

bg %job_number

19. fg – Bring a job to the foreground.

fg %job_number

Disk Usage and Filesystem

20. df – Display disk space usage of file systems.

df -h  # Human-readable format

21. du – Estimate file and directory space usage.

du -sh /path/to/directory  # Total size of a directory

du -ah /path/to/directory  # Display all files and directories sizes

22. mount – Mount a filesystem.

mount /dev/sdX /mnt

23. umount – Unmount a filesystem.

umount /mnt

24. fsck – Check and repair filesystem.

fsck /dev/sdX

Networking

25. ifconfig – Display or configure network interfaces (older tool, replaced by ip).

ifconfig

26. ip – Show/manipulate routing, devices, policy routing, and tunnels.

ip addr show       # Show IP addresses

ip link show       # Show network interfaces

ip route show      # Show routing table

27. ping – Send ICMP ECHO_REQUEST to network hosts.

ping 8.8.8.8       # Ping a public DNS server

28. netstat – Network statistics (use ss on newer systems).

netstat -tuln      # Show listening ports

29. ss – Utility to investigate sockets.

ss -tuln           # Show listening ports and their status

30. wget – Download files from the web.

wget http://example.com/file.txt

31. curl – Transfer data from or to a server.

curl http://example.com

32. scp – Securely copy files between hosts over SSH.

scp file_name user@remote_host:/path/to/destination

System Monitoring and Logs

33. uptime – Show how long the system has been running.

uptime

34. dmesg – Print kernel ring buffer messages (useful for debugging).

dmesg | less

35. journalctl – Query and view logs from systemd journals.

journalctl -xe  # Show system logs

36. tail – View the end of a file.

tail -f /var/log/syslog  # Monitor log file in real time

37. less – View the contents of a file one page at a time.

less /path/to/file

38. grep – Search for patterns within files.

grep "pattern" file_name

grep -r "pattern" /path/to/directory  # Recursively search

User and Group Management

39. useradd – Add a new user.

useradd username

40. usermod – Modify an existing user.

usermod -aG groupname username  # Add user to a group

41. passwd – Change user password.

passwd username

42. groupadd – Add a new group.

groupadd groupname

43. id – Display user and group IDs.

id username

44. whoami – Display the current logged-in user.

whoami

Archive and Compression

45. tar – Archive files.

tar -cvf archive.tar /path/to/directory  # Create archive

tar -xvf archive.tar  # Extract archive

46. gzip – Compress files.

gzip file_name

47. gunzip – Decompress .gz files.

gunzip file_name.gz

48. zip – Compress files into a .zip archive.

zip archive.zip file1 file2

49. unzip – Extract .zip files.

unzip archive.zip

Other Useful Commands

50. sudo – Execute a command as another user (usually root).

sudo command

51. history – Show the command history.

history

52. alias – Create an alias for a command.

alias ll='ls -l'

53. crontab – Schedule tasks (cron jobs).

crontab -e  # Edit cron jobs

These are just a few of the many Linux commands. There are countless others, and each can be customized to suit your specific needs and environment.

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