[Bug 1059827] Re: Non trivial grub2 installs no longer fit in small embed areas

[Chris Bainbridge]

I hit this bug in a different way with 14.04:

Use fdisk to create a new mbr and single partition on a USB-connected drive
mkfs.btrfs the partition
Run installer and select the partition as root, and drive device as grub target

After grub fails the installer exits. fdisk reports the partition starts
at 2048. gdisk reports that the drive has a valid MBR and valid GPT main
header but corrupt GPT backup. At no point did I format the drive as GPT
- I wonder if ubiquity automatically adds a GPT header causing the
subsequent grub install with btrfs to fail?

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https://bugs.launchpad.net/bugs/1059827

Title:
  Non trivial grub2 installs no longer fit in small embed areas

Status in “grub2” package in Ubuntu:
  Triaged
Status in “ubiquity” package in Ubuntu:
  Triaged

Bug description:
  Traditionally the first boot track of the disk was left unpartitioned.
  This area is used to embed the grub2 core.img file.  The size of this
  area used to typically be 62 sectors.  In recent years the typical
  size has changed to 2048 sectors to keep the partitions aligned to a 1
  MiB boundary for performance reasons on SSDs and newer hard disks with
  4KiB sector sizes.  All but the most trivial configurations of grub no
  longer fit in the old 62 sector size embed area.  This results in grub
  complaining that your embed area is unusually small.

  Upstream appears to have no desire to support such configurations, so
  this is unlikely to be fixed, but I will leave this bug report open
  for now.  The workaround for the problem is to repartition the disk
  with modern partitioning tools that will align partitions to 1MiB,
  thus leaving 2048 sectors for the embed area.

  Another workaround is to setup a simple ext4 /boot partition rather
  than try to boot directly from raid or lvm or btrfs.

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