Linux Usermod Command with Examples

Linux usermod command is used to modify or change an existing user’s attributes. User's attributes are home directory, shell, password expiration date, groups, UID etc.

When the command runs, data in the /etc/passwd (user account information), /etc/shadow (secure account information) and /etc/group (group information) files are updated accordingly.

Only root (superuser) can use this command. The basic syntax of this command is as follows.

usermod [-c comment] [-d home_dir [-m]] [-e expire_date] [-f inactive_time]
[-g initial_group] [-G group [,...]] [-l login_name] [-p passwd]
[-s shell] [-u uid [-o]] [-L|-U]login

In this tutorial, we will go through some examples to learn usermod command.

1) Changing home directory of a user

Suppose the current home directory of the user 'test' is /home/test and you want to change it to the existing directory '/home/testnew' without copying the contents of '/home/test', you can use the following command:

# usermod –d /home/testnew test

If you want to move the contents of '/home/test' also (if the new directory doesn’t exist, it will create and move), you need to use the option “-m”.

# usermod –d /home/testnew –m test

2) Adding groups to a user

When a user is added using useradd command without specifying group, then a group with the same name as that of the user will be created. This is the primary group of the user. You can add as many groups to a user using the option -G as follows.

Suppose, you need to add a group 'developer' to the user 'test', you can add it as follows.

# usermod –G developer test

Please note that, if you added the user to any other groups earlier (other than the primary group), that will get removed by the above command.

So, if you want to preserve the current groups of the user and add one more group you need to use the option –aG as follows:

# usermod –aG developer test
# id test
uid=501(test) gid=501(test) groups=501(test),506(pros),508(developer)

3) Changing the primary group of a user

If you want to add a group as the primary group of the user, you can do it as follows:

# usermod –g developer test
# id test
uid=501(test) gid=508(developer) groups=508(developer), 506(pros)

4) Locking and Unlocking users

In some cases, you may need to temporarily lock the account. This can be done with the -L option. This puts a '!' in front of the encrypted password, effectively disabling the password.

# usermod –L test

Users can be unlocked as follows which will remove the ! in front of the encrypted password.

# usermod –U test

5) Changing the expiry data of an account

You can use the following command to disable the account 'test' on '2012-12-01'.

# usermod -e 2012-12-01 test

6) Changing login and password

You can change the login name itself using the -l switch.

# usermod -l newtest test

# id test
Id: test: No such user
# id newtest
uid=501(newtest) gid=508(developer) groups=508(developer), 506(pros)

You can change the password as follows:

# usermod –p newpass newtest

7) Change shell of a user

We can use usermod command to change the shell of a user. The following command will change the shell of the user 'newtest' to '/bin/bash'.

# usermod -s /bin/bash newtest

Read Also:

• How to Add User to Group on Linux
• Linux List Group Members in Linux Terminal