How does sudo configuration work internally in Linux?

Sudo is a powerful command-line utility in Linux that allows users to run programs with the security privileges of another user, typically the superuser (root). The internal workings of sudo are defined by its configuration file, typically located at /etc/sudoers. This file controls the permissions for who can execute commands as other users and under what circumstances.

The sudoers file uses a specific syntax to define rules. Each line in the file represents a single rule and starts with a specification of the user or group, followed by the machine, and then the command that can be executed. Comments can be added with the '#' symbol. There are also aliases that can be defined for users, groups, hosts, and commands to make management easier.

For instance, entries can look like this:

# Allow user 'username' to run all commands as root
username ALL=(ALL) ALL

# Allow group 'admins' to restart the web server
%admins ALL=(root) /usr/sbin/service apache2 restart
    

The sudo command also maintains a log of all commands run and checks for timeout settings for user privileges. This built-in security feature ensures that even if a user has sudo access, there is still a level of auditing and control over what actions they can perform.