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:
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.