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An Overview of the usermod Command and How It's Used
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What is usermod?
Tool Used to Modify a User’s Linux Settings
The usermod
command lets you change an existing Linux user’s settings. Most things that get set up when you create a user — from a login name and home directory to the shell environment — can be altered using usermod
. In addition, usermod
can add a user to supplementary Linux groups, lock and unlock a user’s account, and more. This guide covers how the usermod utility works, and how it relates to other Linux commands.
Comparison to useradd and chmod
The difference between useradd
and usermod
is that the former is used for creating new users and the latter is used for modifying existing users. While useradd
can define a Linux user’s settings, it does so for new users, not existing users. See our Linux Users and Groups
guide for more on the useradd
command.
On the other hand, chmod
, like usermod
, modifies existing resources. But where usermod
modifies settings for an existing user, chmod
modifies the permissions on a given file or directory. For instance, while usermod
allows you to change a user’s home directory, chmod
lets you give a file in that directory executable permissions. Learn more about what chmod
is and how to use it in our guide Modify File Permissions with chmod
.
Using usermod to Add a User to a Group
How to Change a User’s Primary Group with usermod
You can use usermod
to change a user’s primary group with the -g
option. Here is an example:
sudo usermod -g example-group example-user
Take a look at the results with the id
command.
sudo id example-user
uid=1001(example-user) gid=1002(example-group) groups=1002(example-group)
usermod
allows you to assign a user to the groups.How to Add a User to a Group with usermod
To assign a user to one or more supplementary groups, use the -aG
option. This option can assign multiple groups at once, separating each with a comma (no space):
sudo usermod -aG groupA,groupB,groupC example-user
The -a
option is used to have these groups appended to the user’s list of supplementary groups. Without it (using only the -G
option) the user gets removed from any supplementary groups that are not listed in the command.
Below is an example of what the user’s id
information may look like after the command above is executed.
uid=1001(example-user) gid=1002(example-group) groups=1002(example-group),1003(groupA),1004(groupB),1005(groupC)
How do I Use usermod to Change a User’s Home Directory?
Use the -d
option to change the user’s home directory.
sudo usermod -d /home/example-user-new-home example-user
You can add the --move-home
option to also have the contents of the user’s existing home directory moved to the new directory.
sudo usermod --home /home/example-user-new-home --move-home example-user
You can verify the change by echoing the user’s home directory.
echo ~example-user
/home/example-user-new-home
How to Change a User’s Login Name with usermod
usermod
allows you to change a user’s login name with the -l
option, for example:
sudo usermod -l new-example-user example-user
Changing a user’s login name does not change the name of that user’s home directory. Reference the previous section if you want to change the user’s home directory to match its login name.
Running the sudo id example-user
command should now output an error since the user’s login name has changed.
id: ‘example-user’: no such user
How to Lock and Unlock a User’s Account with usermod
You can lock and unlock user accounts with usermod
. Locking an account allows you to prevent logins on it without completely removing the account.
Locking a User’s Account with usermod
To lock a user’s account, use the -L
option.
sudo usermod -L example-user
Locked users display with an exclamation point after their login names, right at the start of their encrypted passwords, in the /etc/shadow
file. The example below displays what an entry for example-user
may look like.
sudo cat /etc/shadow | grep example-user
example-user:![encrypted_password]:[...]
Unlocking a User’s Account with usermod
To unlock a user’s account, use the -U
option.
sudo usermod -U example-user
Now the entry for example-user
in the /etc/shadow
file should lose its exclamation point.
sudo cat /etc/shadow | grep example-user
example-user:[encrypted_password]:[...]
How to Set an Expiration Date for a User’s Account with usermod
To set an expiration date for a user’s account, use the example command. Ensure you replace example-user
with your own user.
sudo usermod example-user -e 2021-07-30
In the above example, the example-user
user account automatically deactivates on July 30, 2021.
sudo chage -l example-user
Last password change : Jun 30, 2021
Password expires : never
Password inactive : never
Account expires : Jul 30, 2021
Minimum number of days between password change : 0
Maximum number of days between password change : 99999
Number of days of warning before password expires : 7
How to Change a User’s Shell with usermod
Use the -s
option with usermod
to define a user’s shell. This option takes a path to the shell’s binary. Leaving the options blank assigns the user the default shell for the system.
Here is an example that assigns the user the Bash shell.
sudo usermod -s /bin/bash example-user
You can then verify the user’s default shell with the following command:
sudo getent passwd example-user
example-user:[...]:/bin/bash
How to Change a User’s UID or GID with usermod
Changing a User’s UID with usermod
You can change a user’s user ID (UID) number with the -u
option. The UID needs to be a unique, non-negative number. Additionally, the number should not fall between 0 and 999, since that range tends to be reserved for system accounts.
sudo usermod -u 1234 example-user
Verify the change with the id
command:
sudo id example-user
uid=1234(example-user) gid=1002(example-group) groups=1002(example-group)
Changing a User’s GID with usermod
Changing a user’s group ID (GID) number takes the same usermod
option as changing a user’s primary group, -g
. Simply provide the group’s GID number instead of its name, as in:
sudo usermod -g 5678 example-user
Remember that the group must already exist — with the intended GID — for this option to work.
Again, you can verify the change with the id
command.
sudo id example-user
uid=1234(example-user) gid=5678(another-example-group) groups=5678(another-example-group)
More Information
You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.
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