Package/process ops · Lesson 19 of 20 · 8 minutes

Package origin review

Compare installed package metadata with package-owned files and change logs.

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Your objectives

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1
Read package origin
Run apt policy fake-nginx.
Hint & worked example
Inspect a fixed training package inventory. The simulator cannot install or upgrade your computer.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
apt policy fake-nginx
```
Remember: Candidate, installed, and repository versions answer different questions.
2
List package-owned files
Run dpkg -L fake-nginx.
Hint & worked example
Inspect installed-package records in the synthetic Debian-style environment.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
dpkg -L fake-nginx
```
Remember: Repository availability and installed package state are separate evidence.
3
Find installation evidence
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.

Understand the pattern

Tracing an installed package to its files and history helps operators explain what they know before they change anything.

apt: Inspect a fixed training package inventory. The simulator cannot install or upgrade your computer.
Candidate, installed, and repository versions answer different questions.
dpkg: Inspect installed-package records in the synthetic Debian-style environment.
Repository availability and installed package state are separate evidence.
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

$ apt policy fake-nginx

fake-nginx:
  Installed: 1.0-training
  Candidate: 1.0-training
  Version table: simulated

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

$ dpkg -L fake-nginx

/usr/sbin/fake-nginx
/etc/fake-nginx
/usr/share/doc/fake-nginx/README

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

$ 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.

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 origin review”, which interpretation is safe?Repository availability and installed package state are separate evidence.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 dpkg workflow from “Package origin review” 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: Process signal evidence Try an incident drill

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