Permissions and users · Lesson 2 of 33 · 9 minutes

Owners and groups

Practice simulated chown and chgrp changes while checking account context.

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 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.
2
Change simulated group
Run chgrp www-data /srv/www/index.html.
Hint & worked example
Change the file group within the permissions of the acting user.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
chgrp www-data /srv/www/index.html
```
Remember: A group name alone does not grant access unless membership and mode bits agree.
3
Verify group
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

Group ownership is a common way teams share access.

groups: List the groups associated with the training user.
Directory search permission also matters when accessing a file inside it.
chgrp: Change the file group within the permissions of the acting user.
A group name alone does not grant access unless membership and mode bits agree.
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

$ groups

learner learners sudo-readonly

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

$ chgrp www-data /srv/www/index.html

group www-data set on /srv/www/index.html

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 “Owners and groups”, 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 group name alone does not grant access unless membership and mode bits agree.

Apply it elsewhere

Before adapting the chgrp workflow from “Owners and groups” 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: Permission review Try an incident drill

Anonymous lesson and mastery progress lasts for this session. Sign in to keep synced lesson XP between sessions; mastery stays device-local. No speed bonus, lost lives, or hint penalties.

Keep learning

GNU Coreutils manual · GNU Bash manual