Permissions and users · Lesson 9 of 33 · 8 minutes

Public and private files

Compare web-readable and private-note permissions.

Open the lab Course map

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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
Inspect public 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.
2
Set public mode
Run sudo chmod 644 /srv/www/index.html.
Hint & worked example
Change permissions using an octal mode or a symbolic adjustment. Each rwx bit belongs to owner, group, or other.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
sudo chmod 644 /srv/www/index.html
```
Remember: Do not use 777 as a blanket fix. Grant the smallest access needed.
3
Set private note
Run chmod 600 /home/learner/notes/todo.txt.
Hint & worked example
Change permissions using an octal mode or a symbolic adjustment. Each rwx bit belongs to owner, group, or other.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
chmod 600 /home/learner/notes/todo.txt
```
Remember: Do not use 777 as a blanket fix. Grant the smallest access needed.

Understand the pattern

Security is context-sensitive; not every file should be locked the same way.

stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents answer different questions.
chmod: Change permissions using an octal mode or a symbolic adjustment. Each rwx bit belongs to owner, group, or other.
Do not use 777 as a blanket fix. Grant the smallest access needed.

Worked example and expected result

$ 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.

$ sudo chmod 644 /srv/www/index.html

(no output; exit 0)

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

$ chmod 600 /home/learner/notes/todo.txt

(no output; exit 0)

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 “Public and private files”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.Do not use 777 as a blanket fix. Grant the smallest access needed.

Apply it elsewhere

Before adapting the chmod workflow from “Public and private files” 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: Protected paths Try an incident drill

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