On Tue 15 Feb 2022 at 14:20:55 (-0500), Felix Miata wrote: > David Wright composed on 2022-02-15 10:11 (UTC-0600): > > > Is anything else required for B to become a "native EFI" installation? > > > This conversion process will, I think, make the system boot into > > the EFI-ed B by default. If I want to make E boot by default again, > > should I boot E and run update-grub and grub-install?³ > > Or should I do this by running efibootmgr? > > Without changing GRUB_DISTRIBUTOR= in /etc/default/grub, you'll wind up with > only > /boot/efi/EFI/debian. It will be just like MBR booting, where the last updated > Grub overwrites what the previous one put in the MBR. I avoid this by > changing the > default > > GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` > > to e.g. > > GRUB_DISTRIBUTOR="bookworm"
That was useful — I hadn't realised the connection between that variable and the directory name in EFI/. It's quite tricky pulling all the threads together: the directory layout in EFI/, all the stuff that's in /sys/firmware/efi/efivars, the efibootmgr's listing, and the contents (and actions) of the EFI menus when you boot into the firmware interface (reached with Esc F9 here, IIRC). > Once you have a unique /boot/efi/EFI/ entry for each installation, you > /should/ be > able to switch which has control either in the BIOS directly, or with > efibootmgr. > Likely update-grub and grub-install would do the same thing, but I've never > given > them the opportunity here. I say /should/ because some UEFI BIOS are finicky > beasts that can't always be trusted to do as expected. > > I avoid the issue of priority usurpation in two ways: > 1-only mount the ESP filesystem to /boot/efi/ on one installation > 2-don't install any bootloader I think I've decided to keep mine simple by: . booting into one primary system from the ESP, . only that primary system has /boot/efi/EFI/ mounted (your 1), . no Grub on the non-primary systems (your 2), . the primary's Grub will choose which system to boot. I'm used to using grubenv for one-time boot selection, even when I'm not at the machine, but am happy to use the EFI menus whenever I need to boot from a stick, etc. > I actually boot from /boot/grub/custom.cfg, by copying /etc/grub.d/40_custom > to > 06_custom. This causes grub-mkconfig to generate a grub.cfg that displays my > custom.cfg entries before its auto-generated entries, minimizing need to > scroll > the menu to find a desired selection. My custom.cfg boots via kernel and > initrd > symlinks (and volume LABEL rather than UUID, same as fstab), so infrequently > has > any need to be updated. Note that my use of singular filenames is inaccurate, > as I > have 5 UEFI systems configured this way, and all have 10 or more Linux > installations. I'll probably go through another iteration of my edgrub script, to reduce even more of the "garbage" in grub.cfg. Thanks for the suggestions. Cheers, David.
