In a Linux file system, what does 'chmod' command change?

The 'chmod' command in a Linux file system is specifically used to change the permissions of a file or directory. In Linux, every file and directory has a set of permissions that dictate who can read, write, or execute the file. The permissions are typically presented in three sets: one for the owner, one for the group, and one for others.

Using 'chmod', an administrator or user can modify these permission settings to allow or restrict access based on these roles. For instance, a user may want to grant execute permission to a script for everyone or limit write access to a specific group of users, all of which can be accomplished using 'chmod'.

Understanding this is crucial because file permissions are an essential part of system security and management in Linux. The command does not alter the file ownership, content, or location, which are handled by other commands like 'chown' for ownership, editing tools for content, and commands like 'mv' for changing locations. Hence, the primary purpose of 'chmod' is to manage and configure file permissions effectively.