fstab entry causes emergency mode to come up

[WhyteHorse]

After upgrading from 14.04 to 14.10 and also from 14.10 to 15.04, the system goes into emergency mode when there is an entry in the /etc/fstab file for a <removable> hard drive that isn't connected. Here's the fstab file that caused it and the HITACHI entry has been commented out which fixed the problem.
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sdb2 during installation
UUID=b7b39e46-3fca-440b-b52e-ced5fa946ac2 / ext4 errors=remount-ro 0 1
# /boot/efi was on /dev/sdb1 during installation
UUID=A0D7-CA74 /boot/efi vfat defaults 0 1
# swap was on /dev/sdb3 during installation
UUID=156b7a15-d9a6-4d90-8f92-bacf916b7515 none swap sw 0 0

#UUID=12EF-3326 /media/ben/HITACHI vfat rw,user,umask=0

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: ubuntu-release-upgrader-core 1:15.04.14
ProcVersionSignature: Ubuntu 3.19.0-25.26-generic 3.19.8-ckt2
Uname: Linux 3.19.0-25-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.2
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Mon Aug 17 10:54:23 2015
InstallationDate: Installed on 2014-09-03 (347 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: dist-upgrade
UpgradeStatus: Upgraded to vivid on 2015-08-17 (0 days ago)
VarLogDistupgradeTermlog:

[Steve Langasek (vorlon)]

What exactly do you mean when you say "emergency mode"?

The expected behavior, when you boot Ubuntu and have a filesystem referenced in /etc/fstab for which the device is absent, is that the system will prompt, via plymouth, whether to continue waiting for the filesystem or to skip mounting it. This should be the case up through Ubuntu 14.10. For Ubuntu 15.04, with the switch to systemd the behavior will be different; but should still not result in the system booting to anything that could be considered "emergency mode".

[WhyteHorse (whytehorse)]

It drops to a shell prompt with a motd that says "Emergency Mode please run <some command> to review the boot logs or else run <some other command> to boot normally". I don't recall the exact text but it's a root shell... In 14.04 it did display the "Press S to skip waiting for filesystem". In 14.10 I went to the grub menu and switched to an older kernel and it worked with the skip message, but the newer kernel just dropped to the shell. In 15.04 the newest kernel dropped to the shell and the older kernel just hung indefinitely.

I removes the fstab entry and the newest kernel boots just fine. That's all I know...

[Steve Langasek (vorlon)]

On Sat, Aug 22, 2015 at 02:25:48AM -0000, WhyteHorse wrote:
> It drops to a shell prompt with a motd that says "Emergency Mode please
> run <some command> to review the boot logs or else run <some other
> command> to boot normally". I don't recall the exact text but it's a
> root shell...

Ok. This appears to be the expected 'emergency' mode with systemd, so for
15.04 and later that is what you would see on a failure to mount a local
filesystem.

> In 14.04 it did display the "Press S to skip waiting for filesystem".

That is also expected.

> In 14.10 I went to the grub menu and switched to an older kernel and it
> worked with the skip message, but the newer kernel just dropped to the
> shell.

This behavior should not vary by kernel. If you can reproduce this error on
a 14.10 system, this would be worth us investigating.

[WhyteHorse (whytehorse)]

I already upgraded so I just have to use recall at this point. From a user's perspective, it would be useful to know why the system dropped to a shell. Perhaps an error message that says "bad entry in /etc/fstab on line 5" or something like that.

[M Purtill (u-7buntu-x)]

 > Ok. This appears to be the expected 'emergency' mode with systemd, so for
 > 15.04 and later that is what you would see on a failure to mount a local
 > filesystem

The thing is, the old behavior was helpful and user-friendly, and the new one is neither. The suggestion to read the long log file is not useful except to an expert (who probably already knows how to read it). Please return to the previous behavior.

[Launchpad Janitor (janitor)]

[Expired for mountall (Ubuntu) because there has been no activity for 60 days.]