21. diff: To find the differences between two files, use diff followed by the file names. For example, diff file1.txt file2.txt will display the lines that differ between “file1.txt” and “file2.txt”.
22. cmp: Use cmp followed by the two file names to check if two files are identical. If there is no output, it means the files are the same. For example, cmp file1.txt file2.txt.
23. comm: comm compares two sorted files line by line and displays lines that are common or unique between the files. Use comm followed by the file names. For example, comm file1.txt file2.txt.
24. sort: To sort the content of a file, use sort followed by the file name. It will display the sorted output. For example, sort myfile.txt.
25. export: To set environment variables, use export followed by the variable name and value. For example, export MY_VAR="Hello".
26. zip: Use zip followed by the archive name and the files/directories you want to zip. For example, zip archive.zip file1.txt file2.txt will create a zip archive containing “file1.txt” and “file2.txt”.
27. unzip: To extract files from a zip archive, use unzip followed by the archive name. For example, unzip archive.zip.
28. ssh: Use ssh followed by the username and the remote host to establish a secure shell connection. For example, ssh username@remote_host.
29. service: To start or stop services in Linux, use service followed by the service name and the action (start, stop, restart, etc.). For example, service apache2 start will start the Apache service.
30. ps: Use ps to display active processes. The command ps aux shows a detailed list of all processes running on the system.
31. kill and killall: To terminate a process, use kill followed by the process ID (PID). For example, kill 1234. killall allows you to terminate processes by name. For example, killall firefox will terminate all Firefox processes.
32. df: Typing df displays disk usage and filesystem information.
33. mount: Use mount to mount file systems in Linux. Provide the device or file system and the mount point. For example, mount /dev/sdb1 /mnt will mount the device /dev/sdb1 to the /mnt directory.
34. chmod: To change file permissions, use chmod followed by the desired permission settings and the file/directory. For example, chmod 755 myfile.txt sets read, write, and execute permissions for the owner, and read and execute permissions for group and others.
35. chown: Use chown followed by the new owner and the file/directory to change ownership. For example, chown newuser myfile.txt changes the owner of “myfile.txt” to “newuser”.
36. ifconfig: Typing ifconfig displays network interfaces and their associated IP addresses.
37. traceroute: Use traceroute followed by the destination IP or domain name to trace the network hops to reach the destination. For example, traceroute google.com will show the network path to reach Google’s servers.
38. wget: To download files from the internet, use wget followed by the URL of the file you want to download. For example, wget https://example.com/file.txt will download “file.txt” from the given URL.
39. ufw: ufw is the uncomplicated firewall command in Linux. You can use it to manage the firewall rules. For example, ufw allow 22 allows incoming SSH connections on port 22.
40. iptables: iptables is the base firewall utility that provides more advanced configuration options for the firewall. It allows you to define specific firewall rules and policies.
41. apt, pacman, yum, rpm: These are package managers used in different Linux distributions. You can use these commands to install, update, or remove software packages. The usage may vary depending on the specific distribution you are using.
42. sudo: To escalate privileges in Linux and execute commands with administrative privileges, prefix the command with sudo. For example, sudo apt-get update will update the package list using elevated privileges.
43. cal: Typing cal will display a command-line calendar for the current month.
44. alias: To create custom shortcuts for regularly used commands, use alias followed by the desired alias name and the command you want to associate with it. For example, alias ll='ls -l' creates an alias “ll” for the command ls -l.
45. dd: dd is used for low-level copying and conversion of data. To create a bootable USB stick, you can use dd to copy the ISO image to the USB device. For example, dd if=image.iso of=/dev/sdb bs=4M will copy the “image.iso” file to the USB device /dev/sdb.
46. whereis: Use whereis followed by the command name to locate the binary, source code, and manual pages for a command. For example, whereis ls will display the location of the “ls” command.
47. whatis: To find a brief description of what a command is used for, use whatis followed by the command name. For example, whatis ls will provide a short description of the “ls” command.
48. top: Typing top displays a live view of active processes, system usage, and resource statistics.
49. useradd and usermod: To add a new user, use useradd followed by the username. For example, useradd newuser creates a new user with the username “newuser”. usermod is used to modify existing user accounts.
50. passwd: To create or update passwords for existing users, use passwd followed by the username. For example, passwd username will prompt you to enter a new password for the specified user.