Ubuntu fails to boot with multipath

[bugproxy]

---Problem Description---
When multipath boot support is on, the system fails to boot. Basically, the UUID device points to the underlying SCSI partition device instead of the multipath partition device when initramfs script tries to mount it.

---uname output---
Linux (none) 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:50:31 UTC 2014 ppc64le GNU/Linux

---Additional Hardware Info---
IPR multipath system.

Machine Type = 8286-42A

---Steps to Reproduce---
Install the system into a multipath device, then install multipath-tools-boot, reboot.

Userspace tool common name: udev

[Launchpad Janitor (janitor)]

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

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2015-02-02 16:26 EDT-------
I will expand a little more on what I found out about the bug, and where it likely is.

As I described in the initial report, the UUID device that is used by the scripts to lookup for the rootfs is pointing out to a SCSI partition device.

For example:

/dev/disk/by-uuid/78c02bb3-9623-4fe0-b283-22f8f3fe8faa -> /dev/sda2

multipath daemon has already detected the multipath setup and created a mapping that uses sda, and creates linear mappings to the partitions using kpartx.

/dev/mapper/mpathap2 -> ../dm-2
/dev/mapper/mpatha -> ../dm-0

The UUID device should point to dm-2 or mpathap2 instead of pointing out to sda2. This is needed because the mpath mapping will grab the device and that will prevent a filesystem to be mounted directly on it.

The UUID device is created by udev. udev is creating that during the device probe. When the multipath partition is created, udev reads the same filesystem UUID there, but can't create the link because it already exists. What needs to be done is removing that link when multipath is detected or sda2 is removed from the system, or forcing the link creation when it already exists.

Cascardo.

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2015-02-06 11:24 EDT-------
*** Bug 120799 has been marked as a duplicate of this bug. ***

[Mauricio Faria de Oliveira (mfo)]

This bug happened due to bug 1004243. Marking as duplicate.

The problem was the /etc/multipath.conf file wasn't copied from installer to disk, as multipath detection failed (/sbin/multipath was missing some dependencies).

The configuration file (essentially enabling user_friendly_names) was required for some reason for the boot to finish properly (possibly the controllers's device names in non-friendly form came up in non-udev-whitelisted form or something, and the boot process got stuck along the way).

As the multipath-tools-boot updated the initramfs without that configuration file (as it didn't exist), the problem happened.