Re: GRUB search doesn't set btrfs subvolume

[Andrei Borzenkov]

On 11.03.2023 22:46, Lyubomir Parvanov wrote:
> > And what is this search command?
> https://www.gnu.org/software/grub/manual/grub/html_node/search.html

I know what grub search command is. You said "call to the search command 
in order to set the prefix environment variable. But as far as I 
understand it doesn't take into account the btrfs subvolumes" and I 
asked you to show this search command invocation.

> > Also show output of
> >
> > lsblk -f
> >
> > NAME               FSTYPE      FSVER LABEL UUID
>        FSAVAIL FSUSE% MOUNTPOINTS
> sda
>
> ├─sda1             vfat        FAT32       CCF8-C7BD
>        504,9M     1% /boot/efi
> ├─sda2             btrfs
> 5f772e81-6e8f-4194-b9b7-5de280170447  256,2M    63% /boot/.snapshots
> │
>                     /boot
> └─sda3             crypto_LUKS 1
> a062052c-fc1f-47f9-bf2d-732f0570a842
>    └─sda3_decrypted btrfs
> b35ef12f-89d2-4449-bf5d-8aef71480809  889,6G     3% /home/.snapshots
>
>                     /home
>
>                     /var/crash
>
>                     /.snapshots
>
>                     /var/log
>
>                     /var/snap/firefox/common/host-hunspell
>
>                     /
>
> > from your operating system where grub.cfg is generated.
> >
> > > as I understand it doesn't take into account the btrfs subvolumes. The
> > prefix
> > > environment variable has the value of (hd0,gpt2)/grub right after
> > dropping
> > > into Minimal bash, and if i manually set the prefix to
> > (hd0,gpt2)/@boot/grub
> > > instead and execute normal, the system boots successfully. What seems
> > > strange to me is that the calls to linux and initrd do in fact detect
> > (and
> > > set) the @boot btrfs subvolume.
> >
> > I do not understand what it means. What exactly "initrd detects and sets
> > @boot" means?
> It somehow knows to include @boot inside the calls to the linux and
> initrd commands
> inside grub.cfg, like so:
> linux /@boot/vmlinuz-5.19.0-35-generic
> root=UUID=b35ef12f-89d2-4449-bf5d-8aef71480809 ro rootflags=subvol=@  quiet
> splash $vt_handoff
>
> Yet it doesn't include @boot in the prefix grub env variable. At least
> that's what i think causes the issue, cause as i said if i set it manually
> in the minimal shell it is able to boot.
>
> I am also attaching the output of findmnt, which might be useful too:
> TARGET                                        SOURCE
>                       FSTYPE      OPTIONS
> /
> /dev/mapper/sda3_decrypted[/@]                    btrfs
> rw,relatime,space_cache=v2,subvolid=256,subvol=/@
> ├─/var/crash
>   /dev/mapper/sda3_decrypted[/@varcrash]            btrfs
> rw,relatime,space_cache=v2,subvolid=262,subvol=/@varcrash
> ├─/home
> /dev/mapper/sda3_decrypted[/@home]                btrfs
> rw,relatime,space_cache=v2,subvolid=257,subvol=/@home
> │ └─/home/.snapshots
>   /dev/mapper/sda3_decrypted[/@home-snapshot]       btrfs
> rw,relatime,space_cache=v2,subvolid=259,subvol=/@home-snapshot
> ├─/.snapshots
> /dev/mapper/sda3_decrypted[/@root-snapshot]       btrfs
> rw,relatime,space_cache=v2,subvolid=258,subvol=/@root-snapshot
> ├─/var/log
>   /dev/mapper/sda3_decrypted[/@varlog]              btrfs
> rw,relatime,space_cache=v2,subvolid=263,subvol=/@varlog
> └─/boot                                       /dev/sda2[/@boot]
>                      btrfs
> rw,relatime,space_cache=v2,subvolid=256,subvol=/@boot
>    ├─/boot/efi                                 /dev/sda1
>                      vfat
>   
> rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
>    └─/boot/.snapshots                          /dev/sda2[/@boot-snapshot]
>                       btrfs
> rw,relatime,space_cache=v2,subvolid=257,subvol=/@boot-snapshot