Could not find the root partition

[lucas-mior]

I've read #52 and #60, tried a lot of things but could not get refind-btrfs to work.
The output:

$ sudo refind-btrfs                    
Initializing the block devices using lsblk.
Initializing the physical partition table for device '/dev/nvme1n1' using lsblk.
Initializing the live partition table for device '/dev/nvme1n1' using findmnt.
Initializing the physical partition table for device '/dev/nvme0n1' using lsblk.
Initializing the live partition table for device '/dev/nvme0n1' using findmnt.
Found the ESP mounted at '/boot' on '/dev/nvme1n1p1'.
ERROR (refind_btrfs.state_management.conditions/conditions.py/check_filtered_block_devices): Could not find the root partition!

/etc/fstab relevant lines:

/dev/mapper/croot1   /                   btrfs noatime,commit=120,compress=zstd:1,discard=async,subvol=/@                  0 0
LABEL=BOOT           /boot               vfat  nofail,noatime,fmask=0133,dmask=0022                                        0 2

/boot/EFI/refind/refind.conf menu entry:

menuentry "Arch Linux - Stable" {
    icon /EFI/refind/icons/os_arch.png
    volume "EFI"
    loader /vmlinuz-linux
    initrd /initramfs-linux.img
    options "root=/dev/mapper/croot1 rw add_efi_memmap rootflags=subvol=@ initrd=\intel-ucode.img"
}

I suspect this problem is because of lsblkfailing to detect all mount points in a btrfs filesystem with multiple subvolumes mounted:

$lsblk /dev/nvme1n1p5 --json --paths --tree | less
{
   "blockdevices": [
      {
         "name": "/dev/nvme1n1p5",
         "maj:min": "259:6",
         "rm": false,
         "size": "1,7T",
         "ro": false,
         "type": "part",
         "mountpoints": [
             null
         ],
         "children": [
            {
               "name": "/dev/mapper/croot1",
               "maj:min": "254:3",
               "rm": false,
               "size": "1,7T",
               "ro": false,
               "type": "crypt",
               "mountpoints": [
                   "/home/lucas/.cache"
               ]
            }
         ]
      }
   ]
}

Note that /dev/mapper/croot1 is actually also mounted to / and /home.

[Venom1991]

This is an LVM setup, if I understand correctly? If so, I didn't develop this tool on an LVM installation and I don't really know why the / partition could not be found. There's probably something different in lsblk's and/or findmnt's outputs which caused the issue.

If you (or anyone with a similar issue) would like to contribute I'd be open to such an arrangement. There are virtually countless possibilities with regards to system setups and there's only one developer, i.e. myself. The problem is, of course, that this tool isn't properly documented and the test coverage is still at 0%. 😌

[lucas-mior]

Yes, it is probably due to lsblk implementation (I edited the issue explaining that). I don't know why, but at some time both btrfs-progs and lsblk changed their reporting of devices.

Previously, btrfs filesystem usage / showed useful device names (/dev/mapper/croot1 and /dev/mapper/croot2), but now it only shows /dev/mapper/dm-1 and /dev/mapper/dm-3 which is generic and does not inform me which device it is talking about.

At the same time, lsblk stopped reporting all mountpoints for a btrfs filesystem, instead it only reports one of them. In this case, another tool for detecting the root partition has to be used. findmnt reports all mountpoints, but the device names are only /dev/dm-3.

But I suggest that the user specifies the root partition manually, in the config file. That is a general and flexible solution, what do you think?

[Venom1991]

But I suggest that the user specifies the root partition manually, in the config file. That is a general and flexible solution, what do you think?

You mean like the possibility to specify the ESP's UUID manually?
I can do it on another branch which you could checkout and try running it on your machine but that's really no guarantee the whole thing would work. I suppose it's worth a try.

[lucas-mior]

I think you wanted to say "specify the ROOT's UUID manually", right? That's exactly what I want. In fact I'm implementing it right now. But if you have it ready I'm willing to test it.

[Venom1991]

I think you wanted to say "specify the ROOT's UUID manually", right? That's exactly what I want. In fact I'm implementing it right now. But if you have it ready I'm willing to test it.

No, I meant to say that you want the same feature that already exists for the ESP to be implemented for /, as well.

EDIT: If you've already started working on it, you may as well try to replicate the existing ESP manual matching feature.

[lucas-mior]

I had basically implemented, but then I noticed that /dev/mapper devices do not have PARTUUIDs. So another persistent block naming has to be used :( which is not so easy as duplicating the ESP feature.

[Venom1991]

Persistent block device naming support is currently missing, that's true.