Add an account
useradd [options] username
-d HOME_DIR home directory of the new account
-g GROUP name or ID of the primary group of the new account
-G GROUPs list of supplementary groups of the new account
-u user ID of the new account
Set password
passwd [options] username
-d delete the password for the named account (root only)
-f force operation
Delete account
userdel [options] username
-f force some actions that would fail otherwise e.g. removal of user still logged in or files, even if not owned by the user
-r remove home directory and mail spool
Modify account
usermod [options] username
-d HOME_DIR new home directory for the user account
-g GROUP force use GROUP as new primary group
-G GROUPs new list of supplementary GROUPS
-a append the user to the supplemental GROUPS mentioned by the -G option without removing the user from other groups
-s new login shell for the user account
-u new UID for the user account
Add a group
groupadd [options] GROUP
-g use GID for the new group
Delete group
groupdel [options] GROUP
-f delete group even if it is the primary group of a user
