$ Linux One Liners
Back to cert prep

Unofficial practice

User, Group, and Permission Check

A command fails with access trouble. Read the user, group, mode, and path traversal evidence before changing ownership or permissions.

Linux One Liners is an independent study and practice resource. It is not affiliated with, endorsed by, or approved by LPI, The Linux Foundation, CompTIA, or any certification provider. This site does not provide exam dumps or real exam questions.

Try first

id app && namei -l /srv/app/current

Troubleshooting ladder

  1. Name the symptom.
  2. Inspect read-only state.
  3. Find the owner, service, file, device, mount, or route.
  4. Read the decisive output field.
  5. Choose the next narrow command.
  6. Avoid broad or destructive changes.
  7. Make the smallest justified change if required.
  8. Verify and record what changed.

drill evidence

Sample output and answer key

Command anatomy

id app && namei -l /srv/app/current
namei -l
show permissions for each path component
stat
show owner, group, mode, and timestamps
id
show the user and group context
target
the exact path or account under review

Annotated output

f: /srv/app/current/.env
drwxr-xr-x root root /
drwxr-xr-x root root srv
drwxr-x--- deploy www-data app
drwxr-x--- deploy www-data current
-rw------- deploy deploy .env

uid=33(www-data) gid=33(www-data) groups=33(www-data)

What to notice

each path segment
where traversal can fail
mode
which read/write/execute bits exist
owner/group
who can access the object
effective user
which account the service actually uses

Safe vs unsafe move

Common wrong move

Only checking the final file and missing an execute bit on a parent directory.

Next safe command

systemctl show nginx -p User -p Group

Goal

Prove the condition with command output before changing the system.

Safe first command

id app && namei -l /srv/app/current

Correct interpretation

The decisive fields are `each path segment`, `mode`, `owner/group`. The affected object is the path, user, address, or package named by the command output. The next safe command is `systemctl show nginx -p User -p Group` because it narrows the evidence without jumping to a broad fix. Watch out for this wrong move: Only checking the final file and missing an execute bit on a parent directory.

Next safe command

systemctl show nginx -p User -p Group

Common wrong move

Only checking the final file and missing an execute bit on a parent directory.

Self-check

Which path component, owner, group, or mode blocks access for the effective user?

source and objective

Related cert objective

Source status: LPI LPIC-1 overview verified July 3, 2026. Current version 5.0; exams 101-500 and 102-500.

Open related practice area

Related command pages

Why this matters

The point is not to memorize a flag. It is to read the evidence, name the next safe check, and avoid the tempting broad fix.