Permissions and users · Lesson 19 of 33 · 8 minutes

Link permission review

Review link metadata and target permissions together.

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
Create key link
Run ln -s ~/.ssh/authorized_keys lab/key-link.
Hint & worked example
Create a symbolic link in the lab with ln -s.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ln -s ~/.ssh/authorized_keys lab/key-link
```
Remember: A relative symlink target is interpreted from the link directory.
2
Read link target
Run readlink lab/key-link.
Hint & worked example
Inspect a symbolic-link target; use resolution options deliberately.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
readlink lab/key-link
```
Remember: A symlink contains a target path, not another copy of the target file.
3
Inspect target mode
Run stat ~/.ssh/authorized_keys.
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 ~/.ssh/authorized_keys
```
Remember: Metadata and file contents answer different questions.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

ln: Create a symbolic link in the lab with ln -s.
A relative symlink target is interpreted from the link directory.
readlink: Inspect a symbolic-link target; use resolution options deliberately.
A symlink contains a target path, not another copy of the target file.
stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents answer different questions.

Worked example and expected result

$ ln -s ~/.ssh/authorized_keys lab/key-link

(no output; exit 0)

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

$ readlink lab/key-link

/home/learner/.ssh/authorized_keys

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

$ stat ~/.ssh/authorized_keys

Path: /home/learner/.ssh/authorized_keys
Type: file
Mode: -rw-------
Owner: learner
Group: learners
Size: 40 bytes

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 “Link permission review”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.A symlink contains a target path, not another copy of the target file.

Apply it elsewhere

Before adapting the readlink workflow from “Link permission review” 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: Permissions checkpoint Try an incident drill

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