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Systems & Data Center · Foundational

usermod

The Linux command that modifies an existing user account, such as groups, shell, home or lock status.

Definition

Key options include -aG to append supplementary groups, -L and -U to lock and unlock, -s to change shell and -e to set an expiry date.

Example

usermod -aG docker alice adds alice to the docker group without removing other groups.

Exam tip

Forgetting -a with -G replaces all supplementary groups, a classic trap.

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