Security administration · Lesson 4 of 35 · 8 minutes

Auth log review

Search training SSH activity for accepted and denied attempts.

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learner@clairos:~ $

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

Your objectives

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1
Read SSH journal
Run journalctl -u ssh.
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
```
Remember: A relevant unit and time range are more useful than an unfiltered wall of logs.
2
Find denied
Run grep denied /var/log/auth.log.
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 denied /var/log/auth.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Find accepted
Run grep accepted /var/log/auth.log.
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 accepted /var/log/auth.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.

Understand the pattern

Security review starts with knowing who got in and who failed.

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.
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

$ journalctl -u ssh

May 26 08:14:02 clairos-learn sshd[104]: publickey accepted for learner
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.

$ grep denied /var/log/auth.log

May 26 08:18:33 clairos-learn sshd[118]: denied password for root
May 26 08:21:44 clairos-learn sshd[141]: denied password for admin

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

$ grep accepted /var/log/auth.log

May 26 08:14:02 clairos-learn sshd[104]: accepted publickey for learner

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

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Firewall baseline Try an incident drill

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