Package/process ops · Lesson 17 of 20 · 8 minutes

Package change evidence

Find package changes and capture an evidence note.

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Your objectives

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1
Capture upgrades
Run grep upgrade /var/log/dpkg.log | tee lab/package-upgrades.txt.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection. Copy a stream both to a file and standard output; -a appends.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep upgrade /var/log/dpkg.log | tee lab/package-upgrades.txt
```
Remember: No matches is exit status 1, which is different from a malformed invocation. tee can overwrite a file even though the output is also visible on screen.
2
Read upgrades
Run cat lab/package-upgrades.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 lab/package-upgrades.txt
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
3
Read openssh 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.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

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.
tee: Copy a stream both to a file and standard output; -a appends.
tee can overwrite a file even though the output is also visible on screen.
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.
dpkg: Inspect installed-package records in the synthetic Debian-style environment.
Repository availability and installed package state are separate evidence.

Worked example and expected result

$ grep upgrade /var/log/dpkg.log | tee lab/package-upgrades.txt

2026-05-26 08:01:00 upgrade fake-openssh 9.9

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

$ cat lab/package-upgrades.txt

2026-05-26 08:01:00 upgrade fake-openssh 9.9

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.

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 change evidence”, which interpretation is safe?A successful first check guarantees that every dependent service is healthy.Reading a source file should precede changing it; avoid printing real secrets.A command appearing in history proves it completed successfully.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Package process expanded checkpoint Try an incident drill

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