usermod

Additional Notes

usermod changes properties of an existing user account. It can change login name, home directory, shell, groups, UID, lock state, and expiration settings.

It is powerful because changing account identity or home paths can affect file ownership, login behavior, and services.

Syntax

usermod [options] username

Parameters

• options: Flags that change how usermod behaves.
• user: User account affected by the command.
• group: Group account affected by the command.
• file: File or directory whose ownership, mode, or access policy is being changed.

Common Options

• -aG GROUPS: Append user to supplementary groups.
• -G GROUPS: Set supplementary groups exactly.
• -s SHELL: Change login shell.
• -d DIR: Change home directory path.
• -m: Move home contents to the new home directory with -d.
• -l NAME: Change login name.
• -u UID: Change numeric UID.
• -L: Lock the user's password.
• -U: Unlock the user's password.
• -e DATE: Set account expiration date.

Examples

sudo usermod -aG docker rani

Add rani to the docker group without removing existing groups.

sudo usermod -s /bin/bash deploy

Change login shell.

sudo usermod -d /srv/deploy -m deploy

Move a user's home directory.

sudo usermod -L guest

Lock a user's password.

groups rani

Check group membership.

Practical Notes

• Use -aG when adding groups. Forgetting -a with -G can remove existing supplementary groups.
• Users usually need a new login session for group changes to apply.
• Be careful changing UID on accounts that already own files.
• Locking a password may not disable every login method, such as SSH keys.