Adding a supplementary group while preserving others | LinuC Level 1 102 Exam original practice question

1.08.1Basic

Add existing user kai to supplementary group docker.

Keep all current supplementary groups.

Which command is appropriate?

Hint 1: Focus on account attributes

Separate account creation, home-directory handling, group membership, login identity, and password state before comparing the commands.

Hint 2: Key terms

Review the short definitions of account records, groups, home directories, shells, and password state involved.

-aG: The usermod combination that appends supplementary groups to existing membership.
Supplementary-group list: The option that sets the supplementary-group list.
-g: The option that changes the primary group.
Supplementary group: An additional group membership beyond the primary group.

Detailed explanation

Correctusermod -aG docker kai

Correct. -aG appends docker to the existing supplementary groups.

Incorrectusermod -G docker kai

Incorrect. -G alone replaces the existing list with docker.

Incorrectusermod -g docker kai

Incorrect. -g changes the primary group.

Incorrectuseradd -aG docker kai

Incorrect. useradd is for creating new users.

An example you can run in a temporary verification environment.

usermod --help | grep -E -- '-a,|-G,'

appendとsupplementary groupsの説明行

Foundation review

Identity attributes such as a user ID, home directory, and login shell.

Primary and supplementary groups used during permission checks.

State and time limits that control password changes and account access.

Question IDKL-102-1021

Environmentshadow-utils usermod help / 状態変更なし

Last technical review2026-08-13

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