Provide way to pass rootflags=degraded (for btrfs)

[Tv]

Right now, /etc/grub.d/10_linux insists on

     GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"

and the only way for me to tell a remote box that booting with a degraded RAID1 for a btrfs root filesystem is via

$ grep degraded /etc/default/grub
GRUB_CMDLINE_LINUX="rootflags=subvol=@,degraded"

but this is brittle because it doesn't do the ${rootsubvol} logic from /etc/grub.d. Please provide a better way.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: grub-common 2.00-13ubuntu3
ProcVersionSignature: Ubuntu 3.8.0-19.29-generic 3.8.8
Uname: Linux 3.8.0-19-generic x86_64
ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
Date: Mon Sep 23 15:19:08 2013
InstallationDate: Installed on 2013-09-23 (0 days ago)
InstallationMedia: Ubuntu-Server 13.04 "Raring Ringtail" - Release amd64 (20130423.1)
MarkForUpload: True
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub2
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[kallisti5 (kallisti5)]

The easy fix here is to change:

GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"

to:

GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol},degraded ${GRUB_CMDLINE_LINUX}"

in /etc/grub.d/10_linux.

Any time your root filesystem is on btrfs, attempting to boot in a degraded state is the best choice to help recovery. You can't rebuild your btrfs raid without swapping disks and running a balance.

[Toby Corkindale (tjc-wintrmute)]

Nearly three years on.. I'm sad to see that even in Ubuntu 16.04 that this bug still exists.

It's quite annoying -- if you have mirrored btrfs drives, you'd really hope that you could boot with a drive missing! (Without having to fiddle around with the grub menu manually)