Security administration · Lesson 8 of 35 · 8 minutes

Incident note

Write a short lab incident note from log evidence.

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
Find denied logins
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
Write incident note
Run echo incident-reviewed > incident-review.txt.
Hint & worked example
Write simple text to standard output. Prefer printf when exact formatting matters.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
echo incident-reviewed > incident-review.txt
```
Remember: Redirection can overwrite an existing file before the command runs.
3
Read incident note
Run cat incident-review.txt.
Hint & worked example
Read one or more files to standard output without editing their contents.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cat incident-review.txt
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.

Understand the pattern

Incident review needs both source evidence and human summary.

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.
echo: Write simple text to standard output. Prefer printf when exact formatting matters.
Redirection can overwrite an existing file before the command runs.
cat: Read one or more files to standard output without editing their contents.
Reading a source file should precede changing it; avoid printing real secrets.

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.

$ echo incident-reviewed > incident-review.txt

(no output; exit 0)

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

$ cat incident-review.txt

incident-reviewed

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 “Incident note”, which interpretation is safe?Redirection can overwrite an existing file before the command runs.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 echo workflow from “Incident note” 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: Exposed services Try an incident drill

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