Capstone labs · Lesson 2 of 18 · 8 minutes

Capstone log sweep

Sweep auth, nginx, and package logs for evidence.

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Your objectives

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1
Find denied auth
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.
2
Read nginx errors
Run tail -n 2 /var/log/nginx-error.log.
Hint & worked example
Show the end of an input; -n selects the number of lines.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
tail -n 2 /var/log/nginx-error.log
```
Remember: This browser lab snapshots output; it does not keep a live tail -f stream.
3
Find package upgrades
Run grep upgrade /var/log/dpkg.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 upgrade /var/log/dpkg.log
```
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.

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.
tail: Show the end of an input; -n selects the number of lines.
This browser lab snapshots output; it does not keep a live tail -f stream.

Worked example and expected result

$ 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.

$ tail -n 2 /var/log/nginx-error.log

May 26 08:10:01 [notice] nginx: using fake static configuration
May 26 08:20:05 [warn] nginx: /api/test returned 404 by design

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

$ grep upgrade /var/log/dpkg.log

2026-05-26 08:01:00 upgrade fake-openssh 9.9

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 “Capstone log sweep”, which interpretation is safe?This browser lab snapshots output; it does not keep a live tail -f stream.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 tail workflow from “Capstone log sweep” 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: Capstone service map Try an incident drill

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