[Bug 686832] [NEW] multipath-tools-boot, root mount failed - Device or resource busy

[Ron]

Public bug reported:

Binary package hint: multipath-tools-boot

After installing "multipath-tools-boot", initramfs fails to mount /root
by uuid with error: "failed: Device or resource busy".  And boot process
falls into (initramfs) prompt.

**Boot/Screen Output:**
Begin: Running /scripts/local-premount ... done.
mount: mounting /dev/disk/by-uuid/082f71b9-47dc-4d4b-bdfa-d5ca61f1e045 on /root
failed: Device or resource busy
Begin: Running /scripts/local-bottom ... done.
done.
<....> other failure messages mounting (dev, sys, proc, etc.) <....>
(initramfs) 


**Further Debugging & Info:**
Procedures & commands, run shortly after (initramfs) prompt appears.
(initramfs) ls -l /dev/disk/by-uuid/
lrwxrwxrwx    1       10 082f71b9-47dc-4d4b-bdfa-d5ca61f1e045 -> ../../dm1
[ This appears correct!?! ]

(initramfs) mount /dev/disk/by-uuid/082f71b9-47dc-4d4b-bdfa-d5ca61f1e045 /root
[ SUCCESS ! ]


**WORKAROUND:**
I have created an initramfs script to slow-down the root mounting attempt:

File: /usr/share/initramfs-tools/scripts/local-top/waitfor-multipath
Content:
#!/bin/sh
VERBOSITY=0
PREREQ="multipath"
prereqs() { echo "$PREREQ"; }
case $1 in
prereqs)
	prereqs
	exit 0
	;;
esac

echo "Waiting 5 seconds for multipaths & udev?? to settle down..."
sleep 5
exit 0
<----END---->

My guess for a general/global bug-fix is multipath-tools-boot script to
include a slight delay/hold-down timer; to allow outside device-mapping
procedures to complete.  ..or a confirmation that dm devices have
finished mapping.


**Observations:**
It appears multipath-tools-boot initramfs script executes successfully VERY quickly, and initramfs scripts continue with attempting to mount the root file system.  Although, dm-# /dev/disk/by-uuid mappings are not instantly ready.  This is why manually typing the same mount command at prompt is immediately successful.

_To duplicate error in a non-boot scenario:_
This exact same behavior can be observed & duplicated on running servers; when mounting a multipath (SAN) volume.  As example; mounting multipath-SAN targets will create: /dev/sda, /dev/sdb, /dev/sdc, etc....   And multipath-tools+devmapper will then create the shared/linked /dev/dm-# mappings.  You are then only supposed to use the /dev/dm-# virtual devices to access multipathed SAN devices (multipaths.)

.... If you then attempt to mount a direct SAN volume /dev/sd?# an error
is raised: "mount: /dev/sd?# already mounted or /<mount_point> busy"


**Software & Versions:**
 OS: Ubuntu 10.10 (Maverick - server)
 Related Packages & versions:
  multipath-tools  0.4.8-14ubuntu4
  multipath-tools-boot  0.4.8-14ubuntu4
  udev  162-2.1
  initramfs-tools  0.98.1ubuntu6
  initramfs-tools-bin  0.98.1ubuntu6
  open-iscsi  2.0.871-0ubuntu5
  open-iscsi-utils  2.0.871-0ubuntu5
  libdevmapper1.02.1  2:1.02.39-1ubuntu6

**Hardware Details:**
 Servers affected: HP Proliant DL385 (G5, G5p, G6) (and others I'm sure.)
 Storage/SAN Type: iSCSI
 Storage/SAN Hardware: HP StorageWorks MSA2312i (and others I'm sure.)
 
 This problem affects servers with iSCSI-boot NICs, AND servers which have a USB-Key with /boot partition.


Please let me know if more information is necessary!

** Affects: multipath-tools (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: by-uuid initramfs iscsi multipath multipath-tools-boot san

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https://bugs.launchpad.net/bugs/686832

Title:
  multipath-tools-boot, root mount failed - Device or resource busy