Managing Users and Groups in Linux

Updated 30 Oct 2012 Read time 3 min(s) 59 sec(s) (392 views). Linux

This simple article provides a list of command-line utilities (including examples) that can be used to manage users and groups on Linux based operating systems. (commands marked ^† require root privilege, or a user with suitable sudo access rights to run).

useradd^†

The useradd command is used to create a new user on a Linux system. (man page here)

Create a new user "testuser1" using default settings as specified in "/etc/default/useradd" and "/etc/skel".
```
root@host# useradd testuser1
```

List defaults used when creating new users

root@host# useradd -D
GROUP=100
HOME=/export/home
INACTIVE=-1
EXPIRE=
SHELL=/bin/sh
SKEL=/etc/skel
CREAT_MAIL_SPOOL=no

Create a new user "testuser2" and set their default shell to "/bin/bash"
```
root@host# useradd -m -s /bin/bash testuser2
```
The -m is specified to create the home directory
Create a new user "testuser3" and specify user id (uid) "1234"
```
root@host# useradd -m -u 1234 testuser3
```

Create a new user "testuser4" and specify group membership

root@host# useradd -m -g group1 -G group2,group3 testuser4

Create a new user "testuser5" and specify it's home directory
```
root@host# useradd -m -d /users/testuser5 testuser5
```

usermod^†

The usermod command is used to modify an existing account on a Linux system. (man page here)

Change a users home directory to "/export/home/testuser1"
```
root@host# usermod -d /export/home/testuser1 testuser1
```
The original users directory is NOT removed.

Add additional groups to an existing user

root@host# usermod -a -G group1,group2,group3 testuser2

Change an existings users default shell to "/bin/zsh"
```
root@host# usermod -s /bin/zsh testuser3
```

userdel^†

The userdel command is used to remove an account on a Linux system. The userdel command will remove any entries for the specified user from "/etc/passwd", "/etc/shadow"/ and "/etc/group". (man page here)

Remove user "testuser1" without removing it's home directory
```
root@host# userdel testuser1
```
Useful if you want to keep the users files online, or if you are archiving them at a later date.
Remove user "testuser2" and it's home directory
```
root@host# userdel -r testuser2
```
Make sure you have a backup of the users home directory just in case.

passwd^†

The passwd command is used to set or change a password for an existing user. The command may also be used for locking and unlocking an account. (man page here)

User "testuser1" changes their own password
```
testuser1@host$ passwd
```
Any user can change their own password in this way.
Change password for "testuser2"
```
root@host# passwd testuser2
```

root

sudo

testuser2@host$ sudo passwd testuser3

Lock user "testuser3" account
```
root@host# passwd -l testuser3
```
Unlock user "testuser4" account
```
root@host# passwd -u testuser4
```
Show password status for all users
```
root@host# passwd -a -S
```
Delete user "testuser5" password
```
root@host# passwd -d testuser5
```

chage^†

The chage command is used to set or change a users password expiry information. (man page here)

Display password expiry for user "testuser1"
```
root@host# chage -l testuser1
```
Change password expiry details interactively for "testuser2"
```
root@host# chage testuser2
```
Force user "testuser3" to change their password at next login
```
root@host# chage -d 0 testuser3
```

groupadd^†

The groupadd command is used for creating a new group on a Linux system. (man page here)

Add a new group "group1"
```
root@host# groupadd group1
```
Add a new group "group2" with a specific group id (gid) "1234"
```
root@host# groupadd -g 1234 group2
```

groupmod^†

The groupmod command is used for modifying a group definition on a Linux system. (man page here)

Change the gid of group "group1"
```
root@host# groupmod -g 1234 group1
```
Change the name of existing group "group2" to "group3"
```
root@host# groupmod -n group2 group3
```

groupdel^†

The groupdel command is used for deleting a group definition on a Linux system. (man page here)

Remove group "group1"
```
root@host# groupdel group1
```

groups

The groups command is used for displaying group membership of a user on a Linux system. (man page here)

User "testuser1" querying which groups the account belongs to
```
testuser1@host$ groups
```
Display groups membership with user "testuser2"
```
root@host# groups testuser2
```

id

The id command is used for displaying a users UID/GID and group membership on a Linux system. (man page here)

User "testuser1" displays their own user and group membership information
```
testuser1@host$ id
```
Display user and group membership information for user "testuser2"
```
root@host# id testuser2
```

Other utilities

pwck, grpck — Utilities that can be used for verification of the password, group and associated shadow files.
gpasswd — Utility for administering the "/etc/group" file.
pwconv, pwunconv — Utilities that can be used for the conversion of passwords to shadow passwords, or back from shadow passwords to standard passwords.

Managing Users and Groups in Linux

useradd†

usermod†

userdel†

passwd†

chage†

groupadd†

groupmod†

groupdel†