Linux user management - Create, Remove, modify an user account

User Management is one of the major responsibilities of a System Administrator. The user can either be an account associated with an application or a human being. This post shows how a user account can be created, removed and modified via CLI.

useradd command

To create a new user in Linux, we use the useradd command. The syntax for useradd command is

useradd [options]username

Important options

-d	set home directory of the new              account
-e	set account expire date
-g	set primary group
-G	set the secondary groups
-s	login shell for new account
-u	set UID

 

examples

To create a new user account named foo with default settings

useradd foo

To create a new user account named foo with primary group as bar

useradd -g bar foo

To create a new user foo, with an additional secondary group admin, type

useradd -G admin foo

To create a user foo with login shell as 'nologin'

useradd -s /sbin/nologin foo

userdel command

To remove a user in Linux, we use the userdel command. The syntax for useradd command is

userdel [options]username

 

examples

To remove a user account foo, type

userdel foo

The above command removes user named foo but the user home directory and mail spool will exist. To remove a user account along with home directory and mail spool, type

userdel -r foo

usermod command

To modify an existing user use the usermod command.The syntax for useradd command is

usermod [options]username

Important options

-a	append new groups to the list of existing secondary groups
-d	modify home directory of a user account
-e	modify account expire date
-g	modify primary group
-G	modify the secondary groups
-L	lock user account
-m	Move the content of the user's home directory to the new location
-s	login shell for new account
-u	set UID
-U	Unlock user account

examples

To modify and move the contents of user foo's home directory from /home/foo to /home/bar, type

usermod -d /home/bar/ -m foo

To forcefully change the primary group of user foo to admin, type

usermod -g admin foo

To modify user foo with secondary group as bar,  type

usermod -G bar foo

To append a new group named calypso, with out removing the existing secondary groups, type

usermod -G calypso -a foo

To temporarily lock a user foo, from logging in

usermod -L foo

There are alternate methods of creating, removing and modifying user accounts, which will be covered in later post. For more options and details about the commands see the respective man pages.