$ Linux One Liners
Back to problems

problem hub

Read-only first

Mount failed from fstab

Verify fstab entries and boot-time mount failures before rebooting or editing storage paths.

Safest first command

findmnt --verify

Before you run this

Expected output: A validation report for `/etc/fstab` entries, including parse errors, missing targets, or dependency problems.

When not to use it: Do not reboot repeatedly on a host with suspect fstab entries; a bad mount can delay boot or drop into emergency mode.

Expected output example

0 parse errors, 0 errors, 0 warnings
Success, no errors or warnings detected

How to read the result

Warnings point to entries that may fail at boot or mount time. A clean verify does not prove remote storage or credentials are reachable.

What to check next

findmnt reports fstab errors

Means: The file has a syntax, target, or option problem.

Next step: Read the failed entry and recent mount logs before editing.

Verify fstab with findmnt

systemctl shows failed mount units

Means: systemd has recorded a mount failure.

Next step: Inspect the failed unit and journal warning lines.

Show Failed Mount Units

Boot warnings mention dependency or timeout

Means: A remote mount, device path, or dependency may be blocking boot.

Next step: Read current boot warnings before retrying.

Read Mount and fstab Warnings

fstab mount decision tree

Verify syntax, inspect failed mount units, then read current boot warnings. Do not keep rebooting until the entry and rollback path are clear.

  1. findmnt --verify
  2. systemctl --failed --no-pager
  3. journalctl -b -p warning --no-pager | grep -iE 'mount|fstab|dependency'

Bad fixes to avoid

Do not comment out storage entries blindly on production hosts. Do not remount read-write or reboot repeatedly when disk, network, or dependency errors are unresolved.

Common causes

  • Bad fstab syntax
  • Missing mountpoint
  • Wrong UUID or device path
  • Network mount timeout
  • systemd dependency failure

What not to change yet

  • Do not reboot until you have a console or rollback path.
  • Do not edit fstab without preserving the original line.
  • Do not ignore read-only or I/O errors.

Stop and escalate if

  • The next step could interrupt users, remove data, or lock out access.
  • The output includes secrets, customer data, or private infrastructure details.
  • You cannot explain the blast radius of the repair command.

supporting commands

Command path

Guides and drills