[Bug 1656369] Re: os-prober will double mount multipath partitions

[Scott Moser]

** Also affects: os-prober (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Also affects: curtin (Ubuntu Xenial)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1656369

Title:
  os-prober will double mount multipath partitions

Status in curtin package in Ubuntu:
  Fix Released
Status in os-prober package in Ubuntu:
  New
Status in curtin source package in Xenial:
  New
Status in os-prober source package in Xenial:
  New

Bug description:
  1. % lsb_release -rd
  Description:	Ubuntu 16.04.1 LTS
  Release:	16.04

  2. % apt-cache policy os-prober
  os-prober:
    Installed: 1.70ubuntu3
    Candidate: 1.70ubuntu3
    Version table:
   *** 1.70ubuntu3 500
          500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          100 /var/lib/dpkg/status

  3. os-prober should skip over multipath partitions

  4. os-prober only skips currently mounted partitions and ends up
  mounting the same filesystem a second time with grub-mount; sometimes
  this results in corrupt reads from /var/lib/os-
  prober/<mount>/boot/grub/grub.cfg  which results in undefined but
  broken behavior

  On multipath systems, you have two block devices pointing to the same
  disk;  when we create and mount a filesytem on one (/dev/sda1) we also
  see the results on a second device (/dev/sdb1)

  grub hooks to calling os-prober which checks /proc/mounts for mounted
  partitions; it skips /dev/sda1, but when checking if /dev/sdb1 is
  mounted, its not listed in /proc/mounts and then continues to call
  grub-mount on /dev/sdb1; this uses grub-fuse to mount the disk a
  second time.

  Even if multipath-tools and the module (dm-multipath) are not loaded,
  it is possible to detect multipath by examining the FSUUID on the
  block devices, blkid for example, will show that /dev/sda1 and
  /dev/sdb1 have the same UUID.

  
  There is a patch for skipping multipath but requires multipathd and the dm-multipath module to be loaded.

  https://build-test.opensuse.org/package/view_file/home:coolo:test/os-
  prober/os-prober-skip-part-on-multipath.patch?expand=1

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: os-prober 1.70ubuntu3
  ProcVersionSignature: Ubuntu 4.4.0-59.80-generic 4.4.35
  Uname: Linux 4.4.0-59-generic x86_64
  NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
  ApportVersion: 2.20.1-0ubuntu2.4
  Architecture: amd64
  CurrentDesktop: GNOME-Flashback:GNOME
  Date: Fri Jan 13 11:17:25 2017
  Dependencies:
   gcc-6-base 6.0.1-0ubuntu1
   libc6 2.23-0ubuntu5
   libgcc1 1:6.0.1-0ubuntu1
  InstallationDate: Installed on 2016-01-01 (378 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20151209)
  SourcePackage: os-prober
  UpgradeStatus: No upgrade log present (probably fresh install)

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