os-prober interrupts device connection of kvm machines

[Kaspar Schiess]

Binary package hint: os-prober

The reported version of os-prober uses mount to mount all block devices in our system. Those block devices are connected iSCSI devices that are used by KVM virtual machines as their root partition. The mount will perform a read-write mount shortly to fsck the device, crippling the root partitions this way. This is confirmed by the man page of mount:

              Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the
              device. For example, Ext3 or ext4 will replay its journal if the filesystem is dirty. To prevent this kind
              of write access, you may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or set the
              block device to read-only mode, see command blockdev(8).

Newer versions of the script (I've looked at 1.47) use blockdev --setro to disable this behaviour. However, doing that will also disable writes for the KVM machines. The guest operating system will not recover from this, even after setting blockdev --setrw again.

The proper way to do things would probably be to use the '-o ro,noload' flag for mount, as documented in the man page and as proposed in the earlier version of this bug: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=556739

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: os-prober 1.38
ProcVersionSignature: Ubuntu 2.6.32-26.48-server 2.6.32.24+drm33.11
Uname: Linux 2.6.32-26-server x86_64
Architecture: amd64
Date: Wed Jun 15 09:02:56 2011
InstallationMedia: Ubuntu-Server 10.04 LTS "Lucid Lynx" - Release amd64 (20100427)
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: os-prober

[Mark Schouten (mark-prevented)]

IMHO, os-prober should skip iscsi devices alltogether. It's very uncommon to boot from iscsi (I think at least), and scanning iscsi-disks will mainly break stuff and cause invalid menuentries.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Mark Schouten (mark-prevented)]

BTW, this might be duplicate with #922765