What is the purpose of the 'chmod' command in Linux?

The primary purpose of the 'chmod' command in Linux is to change file permissions. In Linux and other Unix-like operating systems, every file and directory has associated permissions that determine which users can read, write, or execute the file. The 'chmod' command allows users to modify these permissions for the user, group, and others.

Using 'chmod,' administrators can enable or restrict the permissions for different users, thereby enhancing security and controlling access to sensitive information. For example, one can use 'chmod' to allow only the owner of a file to read or write it while preventing other users from accessing it. This command is fundamental to managing security in a multi-user environment, where different users may have different levels of access to various files.

The other options represent different commands or actions within a Linux environment. Changing directories is handled by the 'cd' command, changing file ownership is accomplished with the 'chown' command, and displaying file contents can be done using commands like 'cat' or 'less.' Each of these commands serves distinct purposes but does not relate directly to modifying the permissions of files.