Linux

Here are some essential Linux commands for a DevOps engineer :

1. ls: Lists files and directories in the current directory.

ls

2. cd: Changes the current directory.

cd /path/to/directory

3. pwd: Prints the current working directory.

pwd

4. mkdir: Creates a new directory.

mkdir new_directory

5. rm: Removes files or directories.

rm file.txt

rm -r directory_name # to remove a directory and its contents

6. cp: Copies files or directories.

cp source_file destination_file

cp -r source_directory destination_directory # to copy directories

7. mv: Moves or renames files or directories.

mv old_name new_name

mv file.txt /path/to/destination

# File Viewing and Editing

8. cat: Concatenates and displays file contents.

cat file.txt

9. less: Views file contents one page at a time.

less file.txt

10. nano: Edits files using the nano text editor.

nano file.txt

11. head: Displays the first few lines of a file.

head file.txt

12. tail: Displays the last few lines of a file.

tail file.txt

# System Monitoring and Management

13. ps: Displays currently running processes.

ps

ps aux # detailed view of all processes

14. top: Displays real-time system information, including processes and resource usage.

top

15. htop: An interactive process viewer (requires installation).

htop

16. df: Reports file system disk space usage.

df -h # human-readable format

17. du: Estimates file and directory space usage.

du -h /path/to/directory # human-readable format

18. free: Displays memory usage.

free -h # human-readable format

19. uptime: Shows how long the system has been running.

uptime

20. who: Displays who is currently logged in.

who

21. uname: Displays system information.

uname -a # detailed system information

# Network Commands

22. ifconfig: Configures and displays network interface information (older command, ip is preferred).

ifconfig

23. ip: Shows/manages IP addresses and routing.

ip addr show

ip route show

24. ping: Checks network connectivity to a host.

ping google.com

25. curl: Transfers data from or to a server.

curl https://example.com

26. wget: Downloads files from the web.

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

27. netstat: Displays network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

netstat -tuln # shows listening ports

28. traceroute: Prints the route packets take to a network host.

traceroute google.com

# File Permissions and Ownership

29. chmod: Changes file permissions.

chmod 755 file.sh # sets read, write, execute for owner; read, execute for group and others

30. chown: Changes file owner and group.

chown user:group file.txt

31. chgrp: Changes group ownership of a file.

chgrp group file.txt

# Compression and Archiving

32. tar: Archives files.

tar -cvf archive.tar /path/to/directory # create an archive

tar -xvf archive.tar # extract an archive

33. zip and unzip: Compresses and decompresses files.

zip -r archive.zip /path/to/directory # create a zip archive

unzip archive.zip # extract a zip archive

34. gzip: Compresses files.

gzip file.txt # compresses file.txt to file.txt.gz

35. gunzip: Decompresses files.

gunzip file.txt.gz # decompresses file.txt.gz to file.txt

# Searching and Finding Files

36. grep: Searches text using patterns.

grep "search_pattern" file.txt

37. find: Searches for files in a directory hierarchy.

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

38. locate: Finds files by name (uses a database).

locate filename

39. which: Shows the full path of shell commands.

which ls

40. whereis: Locates binary, source, and manual page files for a command.

whereis ls

# User Management

41. useradd and userdel: Adds and deletes users.

sudo useradd new_user

sudo userdel old_user

42. passwd: Changes a user's password.

sudo passwd username

43. usermod: Modifies user accounts.

sudo usermod -aG group username # adds user to a group

# System Updates and Package Management (Amazon Linux)

44. yum: Manages packages on Amazon Linux.

sudo yum update # updates package lists and upgrades all packages

sudo yum install package_name # installs a package

45. rpm: RPM package manager.

sudo rpm -i package.rpm # installs a package

sudo rpm -e package_name # removes a package

# Disk Management

46. fdisk: Partition table manipulator for Linux.

sudo fdisk -l # lists disk partitions

47. mkfs: Builds a Linux file system.

sudo mkfs -t ext4 /dev/sdX1 # creates an ext4 file system on the specified partition

48. mount: Mounts a file system.

sudo mount /dev/sdX1 /mnt

49. umount: Unmounts a file system.

sudo umount /mnt

# Miscellaneous Commands

50. echo: Displays a line of text.

echo "Hello, World!"

51. date: Displays or sets the system date and time.

date

52. cal: Displays a calendar.

cal

53. alias: Creates an alias for a command.

alias ll='ls -la'

54. history: Displays the command history.

history

55. clear: Clears the terminal screen.

clear