Security administration · Lesson 18 of 35 · 8 minutes

Package security review

Inspect package metadata during a security review.

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Your objectives

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1
Check openssh policy
Run apt policy fake-openssh.
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-openssh
```
Remember: Candidate, installed, and repository versions answer different questions.
2
Check package status
Run dpkg -s fake-openssh.
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 -s fake-openssh
```
Remember: Repository availability and installed package state are separate evidence.
3
Review package log
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.

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-openssh

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

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

$ dpkg -s fake-openssh

Package: fake-openssh
Status: install ok installed
Version: 1.0-training

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 “Package security 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 security 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: Auth config checkpoint Try an incident drill

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