A user requested that the file permissions on a Linux device be changed to only allow access to a certain group of users. Which of the following commands should be used to complete the user's request?

The `cat` command is used to concatenate and display file content, not to change permissions.

The `chmod` command in Linux is used to change file and directory permissions, allowing the system administrator to specify read, write, and execute access for the owner, group, and others. By adjusting the permissions, access can be restricted to only allow a certain group of users.

The `pwd` command is used to print the current working directory, not to modify file permissions.

`cacls` is a Windows command-line utility for displaying or modifying access control lists (ACLs) for files and folders, not a Linux command.