What command is used to change file permissions?

The command used to change file permissions in Linux is "chmod." This command allows the user to define who can read, write, or execute a file by setting the appropriate permissions. Permissions are specified in either symbolic mode (using letters like read (r), write (w), and execute (x) along with user classes: user (u), group (g), and others (o)) or numeric mode (using octal numbers like 7 for read, write, and execute, 6 for read and write, and so on).

For example, a command like chmod 755 filename sets the permissions so that the user can read, write, and execute the file (7), while the group and others can only read and execute it (5 each). Understanding how to manipulate file permissions is essential for managing security and access rights in a Linux environment.

Other options such as "chown" are used for changing the ownership of a file or directory, while "changeperm" and "modperm" are not standard Linux commands related to file permissions.