How to use the command usermod (with examples)

The usermod command is used to modify a user account on a Linux system. It allows you to change various attributes of a user, such as the username, user ID, user shell, group membership, and home directory.

Use case 1: Change a username

Code:

sudo usermod --login new_username username

Motivation: The motivation for changing a username may be to align it with a user’s real name or to comply with a specific naming convention. It is useful in scenarios where a user wants to update their username without creating a new account.

Explanation:

• --login: This option specifies the new username.
• new_username: The new username that you want to set.
• username: The current username that you want to change.

Example output:

$ sudo usermod --login johnsmith jsmith

This command will change the username of the user “jsmith” to “johnsmith”.

Use case 2: Change a user ID

Code:

sudo usermod --uid id username

Motivation: The motivation for changing a user ID may be to align it with a new system or to manage user privileges. This is useful when a user needs to have a specific user ID.

Explanation:

• --uid: This option specifies the new user ID.
• id: The new user ID that you want to set.
• username: The username of the user whose ID you want to change.

Example output:

$ sudo usermod --uid 1001 jsmith

This command will change the user ID of the user “jsmith” to 1001.

Use case 3: Change a user shell

Code:

sudo usermod --shell path/to/shell username

Motivation: The motivation for changing a user shell may be to provide a different default shell to a user. This is useful when a user wants to use a specific shell for their account.

Explanation:

• --shell: This option specifies the new shell path.
• path/to/shell: The path to the new shell that you want to set.
• username: The username of the user whose shell you want to change.

Example output:

$ sudo usermod --shell /bin/zsh jsmith

This command will change the shell of the user “jsmith” to /bin/zsh.

Use case 4: Add a user to supplementary groups

Code:

sudo usermod --append --groups group1,group2,... username

Motivation: The motivation for adding a user to supplementary groups is to grant additional access rights to specific groups. This is useful when a user needs to be a member of multiple groups to have the necessary permissions.

Explanation:

• --append: This option appends the user to the specified groups instead of replacing the current group membership.
• --groups: This option specifies the list of supplementary groups to add the user to.
• group1,group2,...: The comma-separated list of supplementary groups.
• username: The username of the user you want to add to the groups.

Example output:

$ sudo usermod --append --groups admins,developers jsmith

This command will add the user “jsmith” to the supplementary groups “admins” and “developers”.

Use case 5: Change a user home directory

Code:

sudo usermod --move-home --home path/to/new_home username

Motivation: The motivation for changing a user’s home directory may be to move their files to a different location or to update the user’s workspace. This is useful when a user wants to have their files stored in a different directory.

Explanation:

• --move-home: This option moves the content of the current home directory to the new home directory.
• --home: This option specifies the new home directory path.
• path/to/new_home: The path to the new home directory.
• username: The username of the user whose home directory you want to change.

Example output:

$ sudo usermod --move-home --home /home/new_home jsmith

This command will change the home directory of the user “jsmith” to “/home/new_home” and move the content of the current home directory to the new location.

Conclusion:

The usermod command is a powerful tool for managing user accounts on a Linux system. By using different options and arguments, you can easily modify various attributes of a user, such as the username, user ID, user shell, group membership, and home directory. These use cases demonstrate how to utilize the usermod command to make changes to user accounts efficiently.