Permissions and users · Lesson 28 of 33 · 8 minutes

Least privilege audit

Review identity, service ownership, and sensitive modes.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

learner@clairos:~ $

↑ history · Tab complete · Ctrl+C cancel · Esc, Tab to leaveExit 0

Your objectives

Hints are always available. Wrong turns never cost XP.

1
Show identity
Run id.
Hint & worked example
Inspect user identity and group membership.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
id
```
Remember: A file group is useful only when the acting user belongs to it or has an applicable override.
2
Inspect key
Run stat ~/.ssh/authorized_keys.
Hint & worked example
Inspect a file or directory metadata record, including ownership, permissions, and size.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
stat ~/.ssh/authorized_keys
```
Remember: Metadata and file contents answer different questions.
3
Review service account
Run grep www-data /etc/passwd.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep www-data /etc/passwd
```
Remember: No matches is exit status 1, which is different from a malformed invocation.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

id: Inspect user identity and group membership.
A file group is useful only when the acting user belongs to it or has an applicable override.
stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents answer different questions.
grep: Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
No matches is exit status 1, which is different from a malformed invocation.

Worked example and expected result

$ id

uid=1000(learner) gid=1000(learners) groups=1000(learners),27(sudo-readonly)

Exit status: 0. The command completed successfully in the training fixture.

$ stat ~/.ssh/authorized_keys

Path: /home/learner/.ssh/authorized_keys
Type: file
Mode: -rw-------
Owner: learner
Group: learners
Size: 40 bytes

Exit status: 0. The command completed successfully in the training fixture.

$ grep www-data /etc/passwd

www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin

Exit status: 0. The command completed successfully in the training fixture.

Try a variation

Repeat this workflow in the sandbox with a different scratch filename. Keep the system fixtures unchanged and compare the observed output with your expectation before moving on.

Explain it

In “Least privilege audit”, which interpretation is safe?A successful first check guarantees that every dependent service is healthy.Metadata and file contents answer different questions.A command appearing in history proves it completed successfully.

Apply it elsewhere

Before adapting the stat workflow from “Least privilege audit” to another server, what should you do?Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.Skip output inspection whenever the command is familiar.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Directory traversal modes Try an incident drill

Anonymous lesson and mastery progress lasts for this session. Sign in to keep synced lesson XP between sessions; mastery stays device-local. No speed bonus, lost lives, or hint penalties.

Keep learning

GNU Coreutils manual · GNU Bash manual