On Thu 13 Apr 2023 at 04:14:46 (+0200), Michel Verdier wrote: > Le 12 avril 2023 David Wright a écrit : > > > the menu/ is moot. I would maintain that this failure mode is rare > > enough for a reasonable penalty of having to type a few characters > > editing the Grub menu. > > > > The last time I booted a kernel that was on a different partition > > from my installed Grub, it took no more than typing 23 characters > > and a load of rubouts. (That was after installing bookworm RC1.) > > I agree with all you said. But on this point I don't follow you. Yes the > need is extremely rare. And so I was never able to remember this few > chars stance and each time rely on rescue boot to do this. So I > understand that a simple grub menu could be useful.
When I tried installing bookworm RC1, which I reported in: https://lists.debian.org/debian-user/2023/04/msg00405.html I was left with a system whose Grub menu only contained entries for the new system, because os-prober no longer scours all the other partitions for OSes any more.¹ To get back to booting bullseye by default, the easiest way was to boot bullseye the once, and then run install-grub /dev/sda. So I rebooted, pressed e at the blue Grub screen to edit the first menuitem, and mangled just these lines: set root='hd0,gpt4' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt4 --hint-efi=hd0,gpt4 --hint-baremetal=ahci0,gpt4 21c64c1c-2c0c-4376-922e-40ff9d46d08a else search --no-floppy --fs-uuid --set=root 21c64c1c-2c0c-4376-922e-40ff9d46d08a fi echo 'Loading Linux 6.1.0-7-amd64 ...' linux /boot/vmlinuz-6.1.0-7-amd64 root=UUID=21c64c1c-2c0c-4376-922e-40ff9d46d08a ro quiet echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-6.1.0-7-amd64 to: set root='hd0,gpt5' search --no-floppy --label --set=root ezra05 linux /vmlinuz root=LABEL=ezra05 ro quiet initrd /initrd.img which sufficed to boot the default kernel on my bullseye root partition (via the symlinks, which saves having to know the version). 23 new characters: 5labelezra05LABELezra05, and lots of deletions. Running install-grub then rewrites the BIOS boot partition (/dev/sda1) with bullseye's Grub, overwriting bookworm's. (The MBR gets rewritten too, but it's unchanged.) ¹ I also tested uncommenting GRUB_DISABLE_OS_PROBER=false in /target/etc/default/grub at the point when the d-i first asks: ┌────────────┤ [!] Install the GRUB boot loader ├─────────────┐ This makes os-prober behave as it has done, up until bullseye. Cheers, David.