Package/process ops · Lesson 1 of 20 · 8 minutes

APT installed packages

List simulated installed Linux packages.

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Your objectives

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1
List packages
Run apt list --installed.
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 list --installed
```
Remember: Candidate, installed, and repository versions answer different questions.
2
Show nginx package
Run apt show 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 show fake-nginx
```
Remember: Candidate, installed, and repository versions answer different questions.
3
Search package log
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

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.
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 list --installed

fake-nginx/learn 1.0 installed
fake-openssh/learn 9.9 installed
coreutils/learn 9.5 installed

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

$ apt show fake-nginx

Package: fake-nginx
Version: 1.0-training
Description: simulated package metadata only

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 “APT installed packages”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.Candidate, installed, and repository versions answer different questions.

Apply it elsewhere

Before adapting the apt workflow from “APT installed packages” to another server, what should you do?Skip output inspection whenever the command is familiar.Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: APT package details Try an incident drill

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