[Bug 1562537] Re: Ubiquity installs to 4Kn disk in BIOS mode, but installation won't boot

[Richard Laager]

I can reproduce this in a VM doing a manual install (with debootstrap).
Basically, grub-install works without error, but the system won't boot.
If grub isn't going to work, it'd be nice if it would throw an error in
this case. Also, yes, the installer should be fixed.

** Also affects: grub2 (Ubuntu)
   Importance: Undecided
       Status: New

** Bug watch added: GNU Savannah Bug Tracker #46700
   http://savannah.gnu.org/bugs/?46700

** Also affects: grub via
   http://savannah.gnu.org/bugs/?46700
   Importance: Unknown
       Status: Unknown

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Title:
  Ubiquity installs to 4Kn disk in BIOS mode, but installation won't
  boot

Status in grub:
  Unknown
Status in grub2 package in Ubuntu:
  New
Status in ubiquity package in Ubuntu:
  Confirmed

Bug description:
  A small but increasing number of disks use 4KiB native ("4Kn") sectors
  -- that is, they use 4096-byte physical sectors (which is now common)
  *AND* 4096-byte LOGICAL sectors (which is uncommon, "translation" to
  512-byte sectors being the norm). Today, most 4Kn disks are external
  USB drives; however, a few 4Kn internal disks are now available, such
  as the 8TB HGST 0F23666. Such disks are likely to become more common
  in the future.

  In testing an HGST 0F23666, I've found that the Ubuntu 16.04 beta2
  Ubiquity desktop installer works fine with the disk in UEFI mode on an
  ASUS P8H77-I motherboard; however, in BIOS mode Ubiquity happily
  installs to the disk, but the install Ubuntu then fails to boot. The
  system ran through its POST just fine, but then showed a blinking
  underscore cursor in the top-left corner of the screen; there was no
  GRUB screen or error message.

  In another test using a Dell server computer, a MAAS-mediated BIOS-
  mode install seemed to succeed, but failed on reboot with the same
  symptoms as on the ASUS machine. The identical symptoms suggest either
  a BIOS or GRUB bug.

  I don't know if the problem is in the BIOS or in GRUB; however,
  512-byte sector size assumptions have long riddled the software chain,
  and may never be fixed in BIOSes and CSMs, so even if there's a GRUB
  bug, BIOS/CSM bugs are likely to cause problems on many systems.
  Therefore, it seems prudent to display a prominent warning in Ubiquity
  when it detects a BIOS-mode install that is underway to a 4Kn disk. I
  recommend something along these lines:

  "You appear to be installing to a disk with 4096-byte logical sectors
  in BIOS mode. This installation may not work. A UEFI-based
  installation is more likely to succeed. Continue anyway (Y/N)?"

  The lack of such a warning is likely to result in user frustration
  with failures if/when 4Kn disks become more common.

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