Troubleshooting · Lesson 6 of 26 · 8 minutes

Permission denied triage

Inspect identity and file metadata before changing modes.

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 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.
2
Show groups
Run groups.
Hint & worked example
List the groups associated with the training user.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
groups
```
Remember: Directory search permission also matters when accessing a file inside it.
3
Inspect web file
Run stat /srv/www/index.html.
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 /srv/www/index.html
```
Remember: Metadata and file contents answer different questions.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

whoami: Print the effective user name.
An elevated command can run with a different effective identity from the normal shell.
groups: List the groups associated with the training user.
Directory search permission also matters when accessing a file inside it.
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

$ whoami

learner

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

$ groups

learner learners sudo-readonly

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

$ stat /srv/www/index.html

Path: /srv/www/index.html
Type: file
Mode: -rw-r--r--
Owner: www-data
Group: www-data
Size: 72 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 “Permission denied triage”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.Directory search permission also matters when accessing a file inside it.

Apply it elsewhere

Before adapting the groups workflow from “Permission denied triage” 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: Network listener triage Try an incident drill

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