What is the function of the 'chmod' command?

The 'chmod' command is used in Linux to change the permissions of a file or directory. This command is fundamental for managing access controls in a Unix-like operating system. Permissions determine which users can read, write, or execute a file, and 'chmod' allows system administrators and users to specify these access rights.

When using 'chmod', users can define permissions for the owner of the file, the group associated with the file, and other users. This is accomplished via numeric or symbolic modes, which specify the level of access granted. By effectively utilizing 'chmod', users can protect sensitive information and ensure only authorized access to resources.

Understanding this command is critical for maintaining security and proper access management in a Linux environment. The other options relate to different functions that do not pertain to the modification of file permissions, which confirms the focus on 'chmod' as the primary tool for that purpose.