Security administration · Lesson 30 of 35 · 8 minutes

Security evidence checkpoint

Tie identity, SSH, firewall, and logs into a review.

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

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1
Confirm user
Run whoami.
Hint & worked example
Print the effective user name.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
whoami
```
Remember: An elevated command can run with a different effective identity from the normal shell.
2
Check password auth
Run sudo grep PasswordAuthentication /etc/ssh/sshd_config.
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.
```
sudo grep PasswordAuthentication /etc/ssh/sshd_config
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Review firewall
Run ufw status verbose.
Hint & worked example
Inspect or adjust the training firewall rule list. No real firewall changes occur.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ufw status verbose
```
Remember: Firewall rules should be scoped and reviewed; simulator access is not a production change approval.
4
Read SSH journal
Run journalctl -u ssh -n 2.
Hint & worked example
Read the training journal by unit or a bounded line window.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
journalctl -u ssh -n 2
```
Remember: A relevant unit and time range are more useful than an unfiltered wall of logs.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

whoami: Print the effective user name.
An elevated command can run with a different effective identity from the normal shell.
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.
ufw: Inspect or adjust the training firewall rule list. No real firewall changes occur.
Firewall rules should be scoped and reviewed; simulator access is not a production change approval.
journalctl: Read the training journal by unit or a bounded line window.
A relevant unit and time range are more useful than an unfiltered wall of logs.

Worked example and expected result

$ whoami

learner

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

$ sudo grep PasswordAuthentication /etc/ssh/sshd_config

PasswordAuthentication no

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

$ ufw status verbose

Status: active
Logging: on (simulated)
Default: deny incoming, allow outgoing
- allow 22/tcp
- allow 80/tcp
- allow 443/tcp
- deny 23/tcp

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

$ journalctl -u ssh -n 2

May 26 08:18:33 clairos-learn sshd[118]: password authentication refused
May 26 08:21:44 clairos-learn sshd[141]: root login refused by policy

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 “Security evidence checkpoint”, which interpretation is safe?No matches is exit status 1, which is different from a malformed invocation.A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: SSH client and server policy Try an incident drill

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