On 21/01/2019 11:09, Xi Ruoyao via lfs-dev wrote: > On 2019-01-21 10:44 +0100, Pierre Labastie via lfs-dev wrote: >> Hi, >> >> My machine has an UEFI BIOS, so that I rarely run grub-install. But >> yesterday, >> I built a new qemu VM, with a non-UEFI (virtual) BIOS. When running >> grub-install, it failed with a message (sorry, I haven't saved it) telling >> that it could not find /usr/lib/grub/x86_64-efi. Running "grub-install >> --help" >> returned: >> --------- >> [...] >> --target TARGET install GRUB for TARGET platform [default=x86_64-efi] >> [...] >> --------- >> so I had to run "grub-install --target i386-pc /dev/sda". But now that I have >> done that, "grub-install --help" returns: >> --------- >> [...] >> --target TARGET install GRUB for TARGET platform [default=i386-pc] >> [...] >> --------- >> >> So the default seems to be what is already installed. Checking the source for >> grub-install confirms that. I must have taken a virtual disk used for a >> former >> VM with UEFI BIOS. > > No. Grub 2.02 is detecting the target dynamically at runtime by checking if > /sys/firmware/efi is empty. At first time your system was booted via UEFI so > this is not empty. But at the second time your system was booted via Legacy > BIOS so this is empty.
You are right about the process, but what amazes me is that the first boot was not particularly EFI. I had a DOS partitioning (not GPT), and no /boot/EFI dir, and yet it must have found something in /sys/firmware/efi since it proposed x86_64 as the default (I do have the EFI switches on in the kernel). Well, looks like it will be hard to reproduce. > >> Should we add this switch (--target i386-pc) to the grub-install command in >> the book? > > If the host is booted via UEFI we'll need that to install a non-UEFI Grub. > But I think it's dangerous (may break the booting process of the host). We > should explain this option more seriously (maybe in a "NOTE" or even > "CAUTION"). > Yes, that may break machines with only UEFI boot. I think the command should be written without "--target", as it is now, but a note should be added to explain that the --target option may be used if the wrong if the application default is wrong Pierre -- http://lists.linuxfromscratch.org/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
