Using Fedora 24, I had configured in /etc/fstab an external usb drive:

UUID=6826692e-79f4-4423-8467-cef4d5e840c5 /backup/external      ext4    defaults  0 0

When I unplugged the usb disk and reboot, it does not boot

That is the error message:

[ TIME ] Timed out waiting for device dev-disk-by\x2duuid-6826692e\x2d79f4\x2d4423\x2d8467\x2dcef4d5e840c5.device.
[DEPEND] Dependency failed for /backup/external.
[DEPEND] Dependency failed for Local File Systems.
[DEPEND] Dependency failed for Relabel all filesystems, if necessary.
[DEPEND] Dependency failed for Mark the need to relabel after reboot.

Why does not boot? is it a bug? a feature? of systemd? I know that was a mistake of me, I had to set options to "noauto", but anyway Why booting process stops because a non-critical directory of FHS is missing?

  • 1
    Because it doesn't know what's a critical directory and what's not unless you tell it. All it knows is that there's a filesystem it can't mount. The installer probably should be written to ignore USB on installs to hdd but that's about the most you can do.
    – Bratchley
    Commented Nov 29, 2016 at 13:05
  • So, what's the purpose of FHS? Let's say that external disk drive is broken, why should it stop of booting?
    – sebelk
    Commented Nov 29, 2016 at 13:21
  • Because the system doesn't know if any essential (say "critical") binaries/configfiles are there. The only owner of the knowledge is you, the mounting script haven't implemented basic ai yet. Commented Nov 29, 2016 at 13:25
  • So, the conclusion is: if I set "auto(mount)" systemd thinks is "critical" doesn't it? Or systemd thinks every filesystem is critical unless I told it?
    – sebelk
    Commented Nov 29, 2016 at 13:52
  • 3
    Many distros have support for nofail you might try adding that to the mount options. That way it will mount on boot automatically but only if it's there.
    – Bratchley
    Commented Nov 29, 2016 at 14:35

1 Answer 1


Using the nofail mount option will ignore missing drives during boot. See man pages fstab(5) and mount(8).

nofail Do not report errors for this device if it does not exist.

So your fstab line should instead look like:

UUID=6826692e-79f4-4423-8467-cef4d5e840c5 /backup/external ext4 defaults,nofail 0 0

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