2014/1/10 Chris Murphy <li...@colorremedies.com>: > > On Jan 9, 2014, at 3:03 AM, Michael Chang <mch...@suse.com> wrote: > >> 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. > > Yes I think that will work. Do you agree that a GUI installer permitting, > e.g. /boot on Btrfs raid1, should implement this?
Honestly I'm not clear about the benefit of it on your case (/boot on Btrfs) but it would be helpful if you want managing your config path more in common and general, so use it if you find it useful. :) > Or should it be a future feature of grub-mkconfig to figure out, that two > grub.cfgs are needed? No. I don't think grub-mkconfig should be changed at all. Use it in your UI wrapper scripts to grub-mkcofig would be better. Regards, Michael > > > 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
