Which command is utilized in Linux to modify file permissions?

The command used in Linux to modify file permissions is "chmod," which stands for "change mode." This command allows users to define who can read, write, or execute a file. Permissions in Linux are defined for three distinct categories: the file owner, the group associated with the file, and all other users.

The utility of "chmod" lies in its flexibility; it can be used in symbolic mode (e.g., using letters to specify the permissions such as 'u' for user, 'g' for group, 'o' for others, 'r' for read, 'w' for write, and 'x' for execute) or numeric mode (e.g., using numbers to set the permissions directly). For example, using "chmod 755 filename" sets the owner to read, write, and execute permissions, groups to read and execute, and others to read and execute as well.

This command is essential for managing access controls within a Linux system, ensuring that users have the appropriate level of access to files and directories.