btrfs + lvm + dmcrypt grub command line options

[dns_server]

Binary package hint: debian-installer

Using the 11.4 beta alternate install cd to set up dmcrypt > lvm > btrfs linux will not boot.

The root cause of the problem is btrfs acts different to other file systems and contains sub volumes.
In order to boot when you have a btrfs file system you need to add another option to the linux command line:
rootflags=subvol=@

where @ is the name of the default subvolume.

Below is the lines from a working grub2 config.

menuentry 'Ubuntu, with Linux 2.6.38-8-generic' --class ubuntu --class gnu-linux --class gnu --class os {
        recordfail
        set gfxpayload=$linux_gfx_mode
        insmod part_msdos
        insmod ext2
        set root='(/dev/sda,msdos3)'
        search --no-floppy --fs-uuid --set=root e8d4da23-5cdc-4a53-9cdc-08849f966a55
        linux /vmlinuz-2.6.38-8-generic root=/dev/mapper/vg0-root ro rootflags=subvol=@ quiet splash vt.handoff=7
        initrd /initrd.img-2.6.38-8-generic
}

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: debian-installer (not installed)
ProcVersionSignature: Ubuntu 2.6.38-7.39-generic 2.6.38
Uname: Linux 2.6.38-7-generic x86_64
Architecture: amd64
Date: Wed Apr 6 19:51:23 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha amd64 (20110329.1)
MachineType: Dell Inc. Vostro1710
MemoryUsage:
 total used free shared buffers cached
 Mem: 4058184 2550552 1507632 0 181752 1513692
 -/+ buffers/cache: 855108 3203076
 Swap: 3903484 0 3903484
ProcEnviron:
 LANGUAGE=en_AU:en
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-2.6.38-7-generic root=/dev/mapper/vg0-root ro rootflags=subvol=@ quiet splash vt.handoff=7
SourcePackage: debian-installer
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/18/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A12
dmi.board.name: 0X805C
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnDellInc.:bvrA12:bd03/18/2009:svnDellInc.:pnVostro1710:pvrNull:rvnDellInc.:rn0X805C:rvr:cvnDellInc.:ct8:cvrN/A:
dmi.product.name: Vostro1710
dmi.product.version: Null
dmi.sys.vendor: Dell Inc.