What is the purpose of the 'chmod' command?

The primary purpose of the 'chmod' command is to change file permissions on a Linux system. This command allows users to modify who can read, write, or execute a file. Permissions can be set for three categories of users: the file owner, the group associated with the file, and all other users (often referred to as "others").

Using 'chmod', you can specify permissions numerically (using octal representation) or symbolically (using letters). For example, using 'chmod 755 filename' sets specific read, write, and execute permissions, while using 'chmod u+x filename' adds execute permissions for the user. This command is fundamental for managing access to files and ensuring that only authorized users can perform specific actions, which is crucial for security and proper system functionality.

In contrast, changing file ownership involves the 'chown' command, changing file type is not something done through 'chmod' but rather depends on the file's nature or format, and changing a file name uses the 'mv' command.