Linux Survival Basics
Read-onlyShow Failed Mount Units
A mount failed and you need to see whether systemd has failed mount units.
Command
systemctl --failed --no-pagerBefore you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not reset failed state before capturing the failure.
Expected output
Failed systemd units, including `.mount` units when present.
System impact
Read-only. Nothing changes. The command reads current state and prints diagnostic evidence.
Recovery / rollback: no state is changed.
When to use it
Use after findmnt verification or boot-time mount errors.
When not to use it
Do not reset failed state before capturing the failure.
Example run
Commands shown
These are the commands shown for inspection. Treat them as an example, not proof that your system will behave identically.
systemctl --failed --no-pagersystemctl --failed --no-pager
next steps
Related commands
Show Failed systemd Units
One command tells you which services systemd already knows are broken.
systemctl --failed --no-pager
Check apt Daily Timers
Automatic apt timers can explain locks that seem mysterious.
systemctl list-timers apt-daily* --no-pager
Read the Failure Cause in systemctl Status
The status page often tells you the failed startup step before you open every log.
systemctl status app-worker --no-pager --lines=50
Map systemd Timers to Services
A timer is only half the scheduled job. The service is the payload.
systemctl list-timers --all --no-pager --plain | awk 'NR==1 || /\.timer/ {print $(NF-1), "->", $NF}'
Print the Exact systemd Exit Fields
Turn a noisy service failure into four fields you can paste into an incident note.
systemctl show app-worker --property=Result,ExecMainCode,ExecMainStatus,NRestarts --no-pager
next diagnostic step
Where to go from this command
- Mount failed from fstab hub Use for failed mount unit evidence.
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.