[Bug 1027951] Re: grub-probe does not understand LUKS volumes

[Phillip Susi]

You can create an unlimited number of logical partitions inside the
extended partition.  gptsync is not needed with grub, and it's use is
discouraged as it violates the standards.  When using GPT the only
partition in the MBR is supposed to be the type EE protective partition
covering the whole disk.

To boot a bios based PC from a GPT disk with grub2, you need to create a
small ( 1 MB ) bios_grub partition.

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Title:
  grub-probe does not understand LUKS volumes

Status in “grub2” package in Ubuntu:
  Triaged

Bug description:
  /dev/mapper/vg0-rootlv is a symlink to /dev/dm-2 ("../dm-2").

  When running "grub-probe -d /dev/mapper/vg0-rootlv" it results in this
  error:

      grub-probe: error: no such disk.

  "grub-probe -d /dev/dm-2" outputs "ext2" (it is a ext4 partition).

  I am attaching the strace and ltrace of these calls.

  From the ltrace output it can be seen that using /dev/dm-2 goes into
  calling strcmp and compares "/dev/dm-2" with itself in the end:

      25675 strncmp("sd", "dm-2", 2)                               = 15
      25675 strcmp("/dev/sda", "/dev/dm-2")                        = 15
      25675 strcmp("/dev/sdb", "/dev/dm-2")                        = 15
      25675 __xstat64(1, "/dev/dm-2", 0x7fffe3a77100)              = 0
      25675 malloc(4096)                                           = 0x00ca5f70
      25675 realpath(0x7fffe3a77e3f, 0xca5f70, 0x7fdb1e322720, 22881, 3) = 0xca5f70
      25675 strncmp("sd", "dm-2", 2)                               = 15
      25675 strcmp("/dev/sda", "/dev/dm-2")                        = 15
      25675 strcmp("/dev/sdb", "/dev/dm-2")                        = 15
      25675 strlen("/dev/dm-2")                                    = 9
      25675 malloc(10)                                             = 0x00ca4cd0
      25675 malloc(4096)                                           = 0x00ca6f80
      25675 realpath(0x7fffe3a77e3f, 0xca6f80, 0x7fdb1e322720, 18769, 3) = 0xca6f80
      25675 strncmp("sd", "dm-2", 2)                               = 15
      25675 vasprintf(0x7fffe3a77008, 0x43dec1, 0x7fffe3a76ff0, 0x43cc39, 3) = 9
      25675 malloc(16)                                             = 0x00ca4b60
      25675 malloc(64)                                             = 0x00ca4b80
      25675 malloc(10)                                             = 0x00ca4bd0
      25675 dcgettext(0, 0x439b92, 5, 10, 2)                       = 0x439b92
      25675 dcgettext(0, 0x43a154, 5, 0, 109)                      = 0x43a154
      25675 dcgettext(0, 0x43a51e, 5, 9, 0)                        = 0x43a51e
      25675 strcmp("hd0", "/dev/dm-2")                             = 57
      25675 strcmp("hd1", "/dev/dm-2")                             = 57
      25675 strcmp("/dev/dm-2", "/dev/dm-2")                       = 0

  While when using /dev/mapper/vg0-rootlv it looks different after the
  first line "strncmp(sd, dm-2").

  This issue prevents me from installing Ubuntu on a MacBook Pro (9,2),
  where grub-probe gets used with grub-install.

  The partition table looks as follows, where sda3 should become the
  boot partition and sda4 is a cryptsetup LUKS container (containing a
  LVM):

    Model: ATA APPLE SSD SM256E (scsi)
    Disk /dev/sda: 251GB
    Sector size (logical/physical): 512B/4096B
    Partition Table: gpt

    Number  Start   End    Size   File system  Name                  Flags
     1      20.5kB  210MB  210MB  fat32        EFI system partition  boot
     2      210MB   100GB  100GB  hfs+         Macintosh HD
     3      100GB   101GB  650MB  ext3         /boot                 boot
     4      101GB   251GB  150GB

  I have tried using the latest Grub from Debian (1.99-22.1, without
  success).

  (NOTE: this bug is reported via Apport from another Precise system)

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: grub-pc 1.99-21ubuntu3.1
  ProcVersionSignature: Ubuntu 3.2.0-27.43-generic 3.2.21
  Uname: Linux 3.2.0-27-generic x86_64
  ApportVersion: 2.0.1-0ubuntu11
  Architecture: amd64
  Date: Mon Jul 23 15:21:34 2012
  InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
  SourcePackage: grub2
  UpgradeStatus: No upgrade log present (probably fresh install)

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