groups and group management in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of the command to list all groups on the system?

You run the command cat /etc/group on a Linux system. What will this command output?

Linux CLI

cat /etc/group

A A list of all groups on the system with their members

B The system's hostname

C The current user's groups only

D A list of all user accounts on the system

💡 Hint

Think about where Linux stores group information.

The file /etc/group contains all groups on the system along with their group ID and member users.

💻 Command Output

intermediate

What does the command groups username output?

You run groups alice on a Linux system. What output should you expect?

Linux CLI

groups alice

A All groups on the system

B The primary group of the user 'alice' only

C The user's home directory path

D Groups that the user 'alice' belongs to

💡 Hint

This command shows group memberships for a specific user.

The groups username command lists all groups that the specified user belongs to.

💻 Command Output

advanced

What is the effect of the command sudo usermod -aG sudo alice?

You run sudo usermod -aG sudo alice. What does this command do?

Linux CLI

sudo usermod -aG sudo alice

A Deletes user 'alice' from the system

B Adds user 'alice' to the sudo group without removing existing groups

C Changes 'alice' primary group to sudo

D Removes user 'alice' from the sudo group

💡 Hint

The -a and -G options together modify group membership.

The -a option appends the user to the supplementary groups listed by -G without removing existing groups.

💻 Command Output

advanced

What error occurs when running sudo usermod -G sudo alice if 'alice' is already in groups 'users' and 'staff'?

You run sudo usermod -G sudo alice but 'alice' was previously in groups 'users' and 'staff'. What happens?

Linux CLI

sudo usermod -G sudo alice

A User 'alice' is removed from 'users' and 'staff' groups and only in 'sudo'

B User 'alice' is added to sudo group and keeps all previous groups

C Command fails with syntax error

D User 'alice' is deleted

💡 Hint

The -G option without -a replaces group memberships.

Using -G without -a replaces the user's supplementary groups with the listed ones, removing previous memberships.

🚀 Application

expert

Write a script snippet to add a user to multiple groups safely without removing existing groups

You want to add user 'bob' to groups 'docker' and 'video' without removing his current groups. Which script snippet achieves this correctly?

A sudo usermod -a -G docker -G video bob

B sudo usermod -G docker,video bob

C sudo usermod -aG docker,video bob

D sudo usermod -aG docker bob && sudo usermod -aG video bob

💡 Hint

The -G option accepts a comma-separated list, but appending multiple times requires separate commands.

Option C runs a single command appending both groups at once, ensuring no existing groups are removed. Option C runs two commands appending each group separately, which also works. Option C replaces groups. Option C is invalid syntax.