[Bug 1584442] Re: Bootloader was unable to install during a fresh install alongside windows 10

[Jim Read]

For whatever reason, Windows deployed in BIOS mode. I know, first
instinct is that Windows 10 doesn't support this, but the real story is
it doesn't support BIOS mode with a GPT partition table. What happened
here is that for whatever reason it prioritized keeping your existing
MSDOS parition table from Windows 7 over switching to the new BIOS mode.
This could be because of any number of reasons related to Windows.

Unfortunately, Ubuntu booted in UEFI mode, and so it wants to install
itself the same way. This isn't possible with an MSDOS partition table.

Ubuntu should probably detect this, but for now here are some
workarounds:

Disable UEFI in your bios settings (if possible). Windows likely isn't using it, and if it is you should just be able to turn that back on without any issue.
--OR--
Check your bios settings to see which it prefers: UEFI, or BIOS. If it prefers UEFI, change it to the other way around. This will mean Ubuntu will boot in the correct mode and will try to install to a classic BIOS system.
--OR--
Reformat your entire drive to GPT so that Windows and Ubuntu are both able to use UEFI. Windows  can't install BIOS-Mode to a GPT parition though, so be careful that you don't mess with your system after installing these. You could end up with a bad bios.
----CAUTION----
The last option is VERY DANGEROUS! I have already lost one computer to Windows writing too much to the UEFI partition. My wonderful Lenovo laptop with its awesome keyboard is now a vegetable because the OS detect scripts in the bios were overwritten!

Source:
https://msdn.microsoft.com/windows/hardware/commercialize/manufacture/desktop
/configure-biosmbr-based-hard-drive-partitions

-- 
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Foundations Bugs, which is subscribed to grub-installer in Ubuntu.
https://bugs.launchpad.net/bugs/1584442

Title:
  Bootloader was unable to install during a fresh install alongside
  windows 10

Status in grub-installer package in Ubuntu:
  Confirmed

Bug description:
  Before starting installation ubiquity informed me that the installer
  is started in UEFI mode and that I have one or more operating systems
  which are installed in BIOS compatibility mode. If I continue with the
  installation, I might not be able to boot back into the other
  operating system. This warning is there every time I install any linux
  distro and it finishes the installation correctly and after
  installation I am able to boot back into both OSes installed. The
  installation was successful with all the previous versions of ubuntu
  namely 14.04,15.10 but with the latest LTS, the installer crashed
  saying that the bootloader was not installed at the target.

  The funny thing is, I have windows 10 installed which is a modern OS which needs to be installed in UEFI mode so I do not understand  why I am getting the warning in the beginning of the installation In the first place.
  Mine is an HP Pavilion-G6 laptop.

  EDIT:-I forgot to mention one thing that is, my laptop did not ship
  with windows 10 preinstalled. There was previously windows 7 on my
  laptop which might have been installed in Legacy/BIOS compatibility
  mode. I had upgraded windows 7 to windows 10 but did not need to make
  any changes in the BIOS settings to boot to windows 10. I guess
  windows 10 was able to boot in Legacy mode somehow...Strange. But
  nonetheless, I was able to successfully install previous versions of
  ubuntu in the past along side windows 10 installation

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ubiquity 2.21.63
  ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
  Uname: Linux 4.4.0-21-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  CasperVersion: 1.376
  Date: Sun May 22 18:18:50 2016
  InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu-mate.seed boot=casper quiet splash ---
  LiveMediaBuild: Ubuntu-MATE 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
  ProcEnviron:
   LANGUAGE=en_IN
   PATH=(custom, no user)
   LANG=en_IN
   SHELL=/bin/bash
  SourcePackage: grub-installer
  UpgradeStatus: No upgrade log present (probably fresh install)

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