Failed to start Switch Root

[Andrei-Pozolotin]

1. systemd 237 changed mount behavior

• now it will unmount the sysroot.mount before initrd-switch-root.target

2. this produces boot error in journalctl -e:

Feb 27 10:22:32 work3 systemd[1]: Starting Switch Root...
Feb 27 10:22:32 work3 systemctl[974]: Failed to switch root: Specified switch root path '/sysroot' does not seem to be an OS tree. os-release file is missing.
Feb 27 10:22:32 work3 systemd[1]: initrd-switch-root.service: Main process exited, code=exited, status=1/FAILURE
Feb 27 10:22:32 work3 systemd[1]: initrd-switch-root.service: Failed with result 'exit-code'.
Feb 27 10:22:32 work3 systemd[1]: Failed to start Switch Root.

3. the immediate work around is:

• provide secret> as usual
• observe boot error message
• switch to debug console: CTRL+ALT+F8
• provide manual mount via: mount /dev/mapper/root /sysroot
• continue boot process via: systemctl start initrd-switch-root.service

[MartinX3]

I fixed this issue on my btrfs root with a subvolume rootfs by using btrfs subvolume set-default /.
Somehow the initframfs fstab ignores the subvol=rootfs or subvolid=264 mount option.
Maybe a newer systemD update broke it?

Maybe because I switched from bios boot to uefi boot with efi- and xbootldr partition.
But that doesn't make any sense for me.

Edit: there was an option left in the kernel CMDline overwriting everything I put into the fstab.