2014/1/9 Chris Murphy <li...@colorremedies.com>: > > On Jan 7, 2014, at 10:55 AM, Chris Murphy <li...@colorremedies.com> wrote: > >> >> On Jan 1, 2014, at 10:17 PM, Michael Chang <mch...@suse.com> wrote: >>> >>> We snapshot /boot for kernel and initrd, otherwise the rollback would >>> encounter problem of incompatible userland and kernel/kernel modules. >>> And we need the ability to rollback them in terms of usefulness. >> >> Of course, understood. >> >> core.img is only going to point to one /boot, which may not be the /boot >> snapshot needed for the kernel and initrd. This will be really confusing for >> mortal users. They'd be unlikely to figure it out and understand it, without >> documentation. >> >> If core.img points to the "current" /boot, which it should, that boot has >> the accumulated knowledge of all snapshots, and any recently updated grub >> modules. Choosing to boot a snapshot means using a different /boot for >> kernel/initramfs than what grub is using for its root. I don't off hand see >> a problem with this because it's literally just two files that grub loads >> from a different boot subvolume, found with an absolute path to that >> snapshot. And it also uses rootflags=subvol= to use the matching root >> snapshot. >> >> A separate issue that's not grub's problem is how to deal with the (now >> wrong) fstab entries. systemd looks at fstab and generates mount jobs from >> that; if taught to understand it's booting a snapshot it could second guess >> parts of the fstab. Based on the name of the currently booting root >> snapshot, which systemd definitely knows, it could mount that subvol= >> instead of what's in fstab. It can use name substitution to do the same >> thing with the other subvolume-snapshots that match the root one. Meaning >> all of the snapshots for a system have the same base (re)naming convention. > > Another hiccup. Maybe it's a silly use case. Consider /boot on Btrfs, > multiple-device, raid1 data/metadata profile, UEFI Secure Boot. A drive dies, > and the system needs to be rebooted before a rebuild occurs. > > This works today with /boot on raid1/10 Btrfs. Yes, I manually have to add a > degraded mount option as this isn't automatically done by Btrfs yet. But the > GRUB boot part works. Even degraded, the path to grub.cfg is valid. And the > file system itself keeps multiple copies so there's no work keeping it > current. > > With Secure Boot it's a problem. The signed grubx64.efi has a fixed prefix > location, valid on any computer, to search for grub.cfg, which is on the ESP. > So now we need to have multiple copies of grub.cfg, somehow synced, on each > ESP. Or another solution. If we had a Btrfs subvolumetypeGUID, analogous to > the GPT partitiontypeGUID, and specify that as the baked in partuuid for a > signed grubx64.efi to search for /boot/grub/grub.cfg.
Isn't search --fs-uuid sufficient for this task? Or I'm afraid that I didn't understand your problem enough. cat <<EOF > /boot/efi/EFI/<DISTRIBUTION>/grub.cfg search --fs-uuid --set=root `grub-probe --target=fs_uuid /boot/grub` set prefix=(\$root)/boot/grub configfile \$prefix/grub.cfg EOF grub-mkconfig -o /boot/grub/grub.cfg This way we can avoid calling "grub-mkconfig -o /boot/efi/EFI/<DISTRIBUTION>/grub.cfg" and hopefully can get rid of the problem you have. Regards, Michael > > What do you think? Total edge case? > > > Chris Murphy > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel > _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
