Security administration · Lesson 15 of 35 · 8 minutes

SSH dry run

Inspect SSH client configuration without connecting.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

learner@clairos:~ $

↑ history · Tab complete · Ctrl+C cancel · Esc, Tab to leaveExit 0

Your objectives

Hints are always available. Wrong turns never cost XP.

1
Show SSH version
Run ssh -V.
Hint & worked example
Inspect a fixed SSH training scenario; no real remote connection is made.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ssh -V
```
Remember: Verify host identity and choose credentials deliberately on real systems.
2
Show resolved SSH config
Run ssh -G lab.
Hint & worked example
Inspect a fixed SSH training scenario; no real remote connection is made.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ssh -G lab
```
Remember: Verify host identity and choose credentials deliberately on real systems.
3
Review server password auth
Run sudo grep PasswordAuthentication /etc/ssh/sshd_config.
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.
```
sudo grep PasswordAuthentication /etc/ssh/sshd_config
```
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.

ssh: Inspect a fixed SSH training scenario; no real remote connection is made.
Verify host identity and choose credentials deliberately on real 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.

Worked example and expected result

$ ssh -V

OpenSSH_9.9p1 LearnSSL 1.0 (simulated)

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

$ ssh -G lab

host lab
user learner
hostname clairos-learn-lab
identityfile ~/.ssh/training_key
pubkeyauthentication yes
passwordauthentication no

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

$ sudo grep PasswordAuthentication /etc/ssh/sshd_config

PasswordAuthentication no

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 “SSH dry run”, which interpretation is safe?A successful first check guarantees that every dependent service is healthy.Verify host identity and choose credentials deliberately on real systems.A command appearing in history proves it completed successfully.

Apply it elsewhere

Before adapting the ssh workflow from “SSH dry run” 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: SSH key fingerprint Try an incident drill

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