[Bug 1429327] Re: Boot from an unique, stable, multipath-dependent symlink

Mauricio Faria de Oliveira mauricfo at linux.vnet.ibm.com
Tue May 12 13:40:07 UTC 2015


Hi Mathieu,

(I have no idea what the 3 attachments above are related to. :-)

This is the patch missing for the installer.
I did some testing and noticed some problems w/ it, which made me to reconsider how/if we should really make this based on an UUID= field. Let me describe the issue.

IIRC, if this one is applied, and one or more partitions on multipath disks are used (so there are some UUID=multipath-<uuid> on /etc/fstab), the init jobs for the local filesystems wouldn't finish.
I couldn't investigate further by the time, but I guess the problem is some pieces maybe just don't assume they should pick a symlink from /dev/disk/by-uuid/, and perhaps search for the UUID field in the filesystem itself, which obviously doesn't contain the 'multipath-' prefix).

So, maybe better ways are either to move back to explicitly using
/dev/disk/by-id/ (and then 'multipath-' prefix would be OK, as it's not
a filesystem field, AFAICT), or use different approaches -- I believe
upstream multipath-tools relies on different things, which are probably
worth checking.

I guess that for W, the most interesting thing is to consider moving to
upstream multipath-tools. I know there's a Debian-base to think of (and
I see they still modify the sources to use mpath[0-9]+ rather than
mpath[a-z]+, which creates some difficulties for some backporting..)..
but at some time, either Ubuntu or Debian should make the move to have
better multipath support, and by looking at the number of fixes made
after 0.5.0, I think git HEAD is a very good place to sit on nowadays
(besides it -- VPD page 0x80 as optional -- is important for IBM IPR
controllers..).

This seems something that can span interesting things to talk about :)

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Title:
  Boot from an unique, stable, multipath-dependent symlink

Status in multipath-tools package in Ubuntu:
  In Progress

Bug description:
  -- Problem Description --
  We try to install Ubuntu version 15.04 build 20150218 on our system which use the ibmveth for the network and bluefin (lpfc) for this disks. 
  The Installation completed and ask to continue and reboot, but then it drops to initramfs....
  (initramfs) cat /proc/modules
  usbhid 63247 0 - Live 0xd000000003520000
  hid 128631 1 usbhid, Live 0xd0000000034a0000
  lpfc 778399 1 - Live 0xd000000002e30000
  dm_multipath 25603 0 - Live 0xd000000002cf0000
  scsi_dh 10388 1 dm_multipath, Live 0xd000000002c10000
  scsi_transport_fc 71871 1 lpfc, Live 0xd000000002890000
  (initramfs) cat /proc/cmdline
  BOOT_IMAGE=/vmlinux-3.18.0-13-generic root=/dev/mapper/creeklp1--vg-root ro splash quiet
  Look like it cannot fine the vg-root to boot up. 


    ?????????????????????????? [!!] Partition disks ???????????????????????????
    ?                                                                         ?
    ? Note that all data on the disk you select will be erased, but not       ?
    ? before you have confirmed that you really want to make the changes.     ?
    ?                                                                         ?
    ? Select disk to partition:                                               ?
    ?                                                                         ?
    ?  Multipath mpath0 (WWID 36005076307ffc7b00000000000000717) - 16.1       ?
    ?  Multipath mpath1 (WWID 36005076307ffc7b00000000000000718) - 16.1       ?
    ?  Multipath mpath2 (WWID 36005076307ffc7b00000000000000719) - 16.1   ?   ?
    ?  Multipath mpath3 (WWID 36005076307ffc7b0000000000000071a) - 16.1   ?   ?
    ?  Multipath mpath4 (WWID 36005076307ffc7b0000000000000071b) - 64.4   ?   ?
    ?  SCSI1 (0,0,0) (sda) - 16.1 GB IBM 2107900                          ?   ?
    ?  SCSI1 (0,5,1) (sdaa) - 16.1 GB IBM 2107900                         ?   ?
    ?  SCSI1 (0,5,2) (sdab) - 16.1 GB IBM 2107900                         ?   ?
    ?  SCSI1 (0,5,3) (sdac) - 16.1 GB IBM 2107900                         ?   ?
    ?  SCSI1 (0,5,4) (sdad) - 64.4 GB IBM 2107900                             ?
    ?                                                                         ?
    ?     <Go Back>                                                           ?
    ?                                                                         ?
    ???????????????????????????????????????????????????????????????????????????

  
  conflicting device node '/dev/mapper/mpath4p1' found, link to '/dev/dm-5' will not be created
  conflicting device node '/dev/mapper/mpath4p2' found, link to '/dev/dm-6' will not be created
  conflicting device node '/dev/mapper/mpath4p3' found, link to '/dev/dm-7' will not be created

    ??????????????????????????? [!] Partition disks ???????????????????????????
    ?                                                                         ?
    ? You may use the whole volume group for guided partitioning, or part     ?
    ? of it. If you use only part of it, or if you add more disks later,      ?
    ? then you will be able to grow logical volumes later using the LVM       ?
    ? tools, so using a smaller part of the volume group at installation      ?
    ? time may offer more flexibility.                                        ?
    ?                                                                         ?
    ? The minimum size of the selected partitioning recipe is 596.0 MB (or    ?
    ? 0%); please note that the packages you choose to install may require    ?
    ? more space than this. The maximum available size is 64.2 GB.            ?
    ?                                                                         ?
    ? Hint: "max" can be used as a shortcut to specify the maximum size, or   ?
    ? enter a percentage (e.g. "20%") to use that percentage of the maximum   ?
    ? size.                                                                   ?
    ?                                                                         ?
    ? 64.2 GB______________________________________________________________   ?
    ?                                                                         ?
    ?     <Go Back>                                            <Continue>     ?
    ?                                                                         ?
    ???????????????

  
     ?????????????????????????? [!!] Partition disks ??????????????????????????
     ?                                                                        ?
     ? If you continue, the changes listed below will be written to the       ?
     ? disks. Otherwise, you will be able to make further changes manually.   ?
     ?                                                                        ?
     ? WARNING: This will destroy all data on any partitions you have         ?
     ? removed as well as on the partitions that are going to be formatted.   ?
     ?                                                                        ?
     ? The partition tables of the following devices are changed:             ?
     ?    LVM VG creeklp1-vg, LV root                                         ?
     ?    LVM VG creeklp1-vg, LV swap_1                                       ?
     ?    Multipath mpath4 (WWID 36005076307ffc7b0000000000000071b)           ?
     ?    SCSI1 (0,5,4) (sdad)                                                ?
     ?    SCSI1 (0,0,4) (sde)                                                 ?
     ?    SCSI1 (0,1,4) (sdj)                                                 ?
     ?    SCSI1 (0,2,4) (sdo)                                                 ?
     ?    SCSI1 (0,3,4) (sdt)                                                 ?
     ?                                                                        ?
     ?     <Yes>                                                     <No>     ?
     ?                                                                        ?
     ??????????????????????????????????????????????????????????????????????????




     ????????????????????? [!!] Finish the installation ??????????????????????
     ?                                                                       ?
    ??                         Installation complete                         ?
    ?? Installation is complete, so it is time to boot into your new system. ?
    ?? Make sure to remove the installation media (CD-ROM, floppies), so     ?
    ?? that you boot into the new system rather than restarting the          ?
    ?? installation.                                                         ?
    ??                                                                       ?
    ??     <Go Back>                                          <Continue>     ?
     ?                                                                       ?
     ?????????????????????????????????????????????????????????????????????????

  
  creeklp2 is now booting. I made a few changes to the system to accomplish this.

  First I got the machine to boot by doing the following from the
  initramfs:

  1. modprobe scsi_dh_alua
  2. multipath -v0
  3. exit

  Once the machine was booted, I did the following:

  1. Added scsi_dh_alua to /etc/initramfs-tools/modules
  2. Ran update-initramfs to update the initramfs with this change
  3. Set GRUB_DISABLE_LINUX_UUID=true in /etc/default/grub
  4. Rebuild grub.cfg by using grub-mkconfig

  I'm still getting a lot of errors booting the system from udev due to
  the fact that udev is spawning a call to multipath for each /dev/sd
  device on the system.

  I decided to change to not use UUID when I saw in the initramfs that
  the /dev/disk/by-uuid symlink was pointing to one of the paths of the
  multipath device rather than the multipath device itself.

  It seems there may be some udev configuration issues here when booting
  from a multipath device.

  Can we get someone from Canonical to take a look at this?

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