Which command is used to change the permissions of a file in Linux?

• A. chmod
• B. kill
• C. ping
• D. ln

Answer: (A)

The command used to change the permissions of a file in Linux is "chmod." This stands for "change mode" and allows users to define who can read, write, or execute a file. Through this command, file permissions can be modified by specifying the user type (owner, group, others) and the desired permissions (read, write, execute) using symbolic (e.g., u+r for adding read permission to the user) or octal (e.g., 755) notation.

The other commands relate to different functionalities: "kill" is used to terminate processes, "ping" checks connectivity between hosts on a network, and "ln" is used to create links between files. None of these commands serve the purpose of changing file permissions, which is why they are not correct answers.