EX200 Manage users and groups Practice Question
Exhibit
# cat /etc/group root:x:0:root bin:x:1:bin,daemon daemon:x:2:bin,daemon sys:x:3:root,bin,adm adm:x:4:root,daemon,adm tty:x:5: disk:x:6:root lp:x:7:daemon,lp mem:x:8: kmem:x:9: wheel:x:10:root,alice,bob ssh_keys:x:101: sshd:x:74: alice:x:1001: bob:x:1002:
Refer to the exhibit. A user named 'carol' has been added to the system with the command useradd -G wheel carol. Which line in /etc/group will confirm that carol is now a member of the wheel group?
⚠ Common exam trap
In Red Hat Enterprise Linux, the /etc/group file format requires member lists to be comma-separated with no trailing comma, and the useradd -G command appends users to the end of the supplementary group member list.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
wheel:x:10:root,alice,bob,carol
The `useradd -G wheel carol` command adds 'carol' to the supplementary group 'wheel', and the `/etc/group` file lists supplementary members as a comma-separated list with no trailing comma. The line `wheel:x:10:root,alice,bob,carol` shows 'carol' appended after the existing members, which matches the expected format.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
wheel:x:10:carol,root,alice,bob
Why it's wrong here
Incorrect. Although 'carol' appears in this line, the order is different and the list does not match the typical output of `useradd -G`. The `-G` option appends the user to the supplementary group list, so 'carol' should appear at the end, following the existing members 'root,alice,bob'. Additionally, option A places 'carol' first, which is not the default behavior of `useradd -G` on Red Hat systems.
- ✓
wheel:x:10:root,alice,bob,carol
Why this is correct
Correct. The `useradd -G wheel carol` command adds 'carol' to the supplementary group 'wheel' by appending her username to the end of the comma-separated member list in `/etc/group`. The line `wheel:x:10:root,alice,bob,carol` shows 'carol' after the existing members, with no trailing comma, which is the correct format.
- ✗
wheel:x:10:root,alice,bob,carol,
Why it's wrong here
A trailing comma after the last member creates an extra, empty field in the /etc/group member list. The standard format for the group file is a comma-separated list with no empty entries, so wheel:x:10:root,alice,bob,carol, is invalid and would be rejected or misinterpreted by utilities that parse /etc/group. When useradd -G appends a user to a group, it writes the username directly after the last existing member, never with a trailing separator.
- ✗
wheel:x:10:root,alice,bob carol
Why it's wrong here
The /etc/group file uses commas as the sole delimiter between member account names; spaces are not valid separators and are treated as characters within a username. In wheel:x:10:root,alice,bob carol, the tool would attempt to interpret 'bob carol' as a single username, which cannot exist because usernames cannot contain spaces. The output generated by useradd -G always places a comma immediately before each new member, never a space, so this line could not result from the command.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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