Permissions and users · Lesson 3 of 33 · 9 minutes

Permission review

Review sensitive training SSH and web files with long listings and metadata.

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learner@clairos:~ $

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Your objectives

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1
List SSH config
Run ls -l /etc/ssh.
Hint & worked example
List directory entries; -a includes hidden names and -l adds ownership and permission detail.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ls -l /etc/ssh
```
Remember: A listing is not proof that you can read or modify every listed file.
2
Inspect sshd_config
Run stat /etc/ssh/sshd_config.
Hint & worked example
Inspect a file or directory metadata record, including ownership, permissions, and size.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
stat /etc/ssh/sshd_config
```
Remember: Metadata and file contents answer different questions.
3
Check root login
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.

Understand the pattern

Reviews find risky permissions before they become incidents.

ls: List directory entries; -a includes hidden names and -l adds ownership and permission detail.
A listing is not proof that you can read or modify every listed file.
stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents 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

$ ls -l /etc/ssh

--rw------- root root    69 sshd_config

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

$ stat /etc/ssh/sshd_config

Path: /etc/ssh/sshd_config
Type: file
Mode: -rw-------
Owner: root
Group: root
Size: 69 bytes

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

$ sudo grep PermitRootLogin /etc/ssh/sshd_config

PermitRootLogin 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 “Permission review”, which interpretation is safe?Metadata and file contents answer different questions.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 stat workflow from “Permission 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: Numeric modes Try an incident drill

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