Capstone labs · Lesson 9 of 18 · 8 minutes

Capstone hardening review

Tie hardening settings to exposure and identity.

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learner@clairos:~ $

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Your objectives

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1
Check root policy
Run sudo grep PermitRootLogin /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 PermitRootLogin /etc/ssh/sshd_config
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
2
Check listeners
Run ss -tulpn.
Hint & worked example
Inspect simulated listening sockets and connection information.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ss -tulpn
```
Remember: A listening socket is not proof of correct application responses or external reachability.
3
Confirm user
Run whoami.
Hint & worked example
Print the effective user name.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
whoami
```
Remember: An elevated command can run with a different effective identity from the normal shell.

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.
ss: Inspect simulated listening sockets and connection information.
A listening socket is not proof of correct application responses or external reachability.
whoami: Print the effective user name.
An elevated command can run with a different effective identity from the normal shell.

Worked example and expected result

$ sudo grep PermitRootLogin /etc/ssh/sshd_config

PermitRootLogin no

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

$ ss -tulpn

Netid State  Local Address:Port  Process
udp   UNCONN 0.0.0.0:68          lab-dhcp
tcp   LISTEN 0.0.0.0:22          sshd
tcp   LISTEN 0.0.0.0:80          nginx
tcp   LISTEN 0.0.0.0:443         nginx

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

$ whoami

learner

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 “Capstone hardening review”, which interpretation is safe?A listening socket is not proof of correct application responses or external reachability.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 ss workflow from “Capstone hardening 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: Final operator check Try an incident drill

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