A collection of users which can be used to help manage users, such as assigning and revoking permissions to files and directories.
group
Creates a new group.
groupadd
Modifies a group definition
groupmod
Deletes a group.
groupdel
Changes a group password.
gpasswd
Changes your current or real group ID to the group ID specified in the command
newgrp
Modifies group membership for the user account
usermod
Displays the primary and secondary group membership for the specified user account.
groups