Text and logs · Lesson 12 of 38 · 7 minutes

Package log basics

Inspect simulated package activity without installing anything.

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Your objectives

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1
Search install
Run grep install /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 install /var/log/dpkg.log
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
2
Tail package log
Run tail -n 2 /var/log/dpkg.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/dpkg.log
```
Remember: This browser lab snapshots output; it does not keep a live tail -f stream.
3
Count package log
Run wc -l /var/log/dpkg.log.
Hint & worked example
Count input. -l counts newline characters, -w counts whitespace-delimited words, and -c counts bytes.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
wc -l /var/log/dpkg.log
```
Remember: Text without a final newline may have fewer counted lines than visible rows.

Understand the pattern

Recent package changes can explain new failures.

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.
wc: Count input. -l counts newline characters, -w counts whitespace-delimited words, and -c counts bytes.
Text without a final newline may have fewer counted lines than visible rows.

Worked example and expected result

$ grep install /var/log/dpkg.log

2026-05-26 08:00:00 install fake-nginx 1.0
2026-05-26 08:02:00 status installed fake-nginx 1.0

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

$ tail -n 2 /var/log/dpkg.log

2026-05-26 08:01:00 upgrade fake-openssh 9.9
2026-05-26 08:02:00 status installed fake-nginx 1.0

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

$ wc -l /var/log/dpkg.log

2 /var/log/dpkg.log

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 “Package log basics”, 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 “Package log basics” 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: Access log review Try an incident drill

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