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Grub doesn't install in Ubuntu 18.04 64 bits (sdb2) because my Windows Pro 7 is in 32 bits (sdb2). Flash drive for boot Ubuntu in UEFI bios, my OS installed are in legacy bios. When I installed grub, I got this error:

$ grub-install --root-directory=/mnt/dev/sda
Installing for i386-pc platform.
grub-install: error: failed to get canonical path of `/mnt/boot/grub'

After try grub repair and use the commnad:

ubuntu@ubuntu:~$ sudo update-grub
/usr/sbin/grub-probe: error: failed to get canonical path of `/cow'.

Any idea how to recover at least Windows 7 Pro, without a backup of W7Pro? Only have W7 home (32 and 64bits).

Again using boot repair it send me that:

http://paste.ubuntu.com/p/T9D5W93RR5/

http://paste.ubuntu.com/p/fm4SXZM2J7/

After use boot-repair I got Windows 7 Pro back (32 bits, MBR in sda1). Now I don't know how get Ubuntu 18.04 (64 bits, sdb1) Sounds that grub2 can't work with one OS 32 bits and another 64 bits. As I didn't create any gpt partition, only had used the old partition table (erasing the \ and \home to install Ubuntu 18.04 64 bits, with flash drive bootable). Ubuntu 18.04 couldn't be in UEFI mode (???)

My flash drive was created in Ubuntu Trusty Tahr 32 bits and I don't know why it is as UEFI flash drive.

Reading others topics, seen even if I reinstall grub and it works with both systems in different architectures, when I have to update the system, the problem will come back. I also don't want to use Easy BCD creator.

After. installation of Ubuntu I received the message that grub could 't be install.

I used commands from topics I'd read. I know that such commands must be used with sudo. Grub repair had created a boot partition in sdb1 but it also doesn't workout
By the way I already had to reinstall and edit grub in older versions of Ubuntu using Live DVD and everything was fine. The problem sounds to happen because differences between two different architecture. My Debian Wheeze is also 32 bits.

Now I will download the .iso of Ubuntu 18.04 again and recreate with rufus the bootable flash drive to avoid UEFI system. Reinstall Ubuntu 18.04 64 bits without any kind of UEFI system.

I solve the problem. It was the flash drive in Uefi. I download the iso and created a bootable pendrive with Rufus for Mbr boot instead efi. The only silly thing was to download the wrong Ubuntu iso (18.10): Md5sum was always wrong. Although I did instal that version anyway. Until the beginning of live Ubuntu it's more friendly. Sorry for so many fool questions. Thanks for all who helped me.

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  • Try this Link
    – Vijay
    Oct 24, 2018 at 13:26
  • AFAIK you don't install grub to a mount point as you're doing, grub most install the device, not a partition or mount point. Oct 26, 2018 at 14:53
  • In other words, you should install grub to /dev/sdb but what you're doing is trying to install it inside the some mount point you've set for the partition. I've never seen anything like that before lol Oct 26, 2018 at 14:54
  • Do not run auto repair in Boot-Repair, you want to keep a Windows boot loader on the Windows drive. Use the advanced mode and choose Linux install and sdb drive for install of grub. Separately you have a new UEFI based system, but running 32 bit BIOS/MBR configurations?
    – oldfred
    Oct 26, 2018 at 14:58
  • Seems like you're also issuing the grub-install and update-grub commands with no administrative rights... Are you sure you know what you're doing? Because, I mean, I can't say for installing grub on a thumb drive because I've never tried that but at least on an HDD it's super easy. You just do grub-install /dev/sda, but in your case you should mount the boot partition of your Linux distro and point that to grub installer, which is what I think Is what you were trying to do. Oct 26, 2018 at 15:05

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Seems like you're also issuing the grub-install and update-grub commands with no administrative rights... Are you sure you know what you're doing? Because, I mean, I can't say for installing grub on a thumb drive because I've never tried that but at least on an HDD it's super easy. You just do grub-install /dev/sda, but in your case you should mount the boot partition of your Linux distro and point that to grub installer, which is what I think Is what you were trying to do.

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  • Regarding your request for this to be deleted, this has been accepted as an answer. If you would prefer to expand this into an actual answer, you may, however because this has already been marked as 'accepted' by the OP, I'm not going to delete this at this time.
    – Thomas Ward
    Oct 30, 2018 at 13:35
  • @ThomasWard I'll expand it later. Oct 30, 2018 at 13:37

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