#803625 grub-common: 10_linux doesn't merge rootflags= from GRUB_CMDLINE_LINUX*

Package:
grub-common
Source:
grub2
Description:
GRand Unified Bootloader (common files)
Submitter:
Christoph Anton Mitterer
Date:
2021-03-25 15:33:11 UTC
Severity:
important
#803625#5
Date:
2015-11-01 05:34:20 UTC
From:
To:
Hi.

That's basically a follor-up or at least related to #803624.

When the root-fs is on a btrfs subvolume (and perhaps in other cases
as well), 10_linux adds a rootflags= to the kernel parameters, not
merging any possibly already set such option in
GRUB_CMDLINE_LINUX_DEFAULT or GRUB_CMDLINE_LINUX.


Now coming back to my degraded-RAID-should-still-boot scenario from
#803624, even when I manually set GRUB_CMDLINE_LINUX=rootflags=degraded
things won't work (and the boot fails when a disk is e.g. missing).

It results in a grub.cfg line like:
  linux   /root/boot/vmlinuz-4.2.0-1-amd64 root=UUID=d430d7ee-8059-11e5-9834-502690aa641f ro rootflags=subvol=root rootflags=degraded
and apparently the 2nd rootflags= is simply ignored.


When I manually change the line to:
  linux   /root/boot/vmlinuz-4.2.0-1-amd64 root=UUID=d430d7ee-8059-11e5-9834-502690aa641f ro rootflags=subvol=root,degraded
everything works (even though I don't know what would happen if there was a subvolume named "root,degraded",
so perhaps one needs some quoting in that case?).


Any ideas?

Cheers,
Chris.
#803625#10
Date:
2021-03-25 15:18:33 UTC
From:
To:
 > It results in a grub.cfg line like:
 > linux /root/boot/vmlinuz-4.2.0-1-amd64
root=UUID=d430d7ee-8059-11e5-9834-502690aa641f ro rootflags=subvol=root
rootflags=degraded
 > and apparently the 2nd rootflags= is simply ignored.

My tests shows that first "rootflags" is ignored, and the second one
matters:


root@pegaz# cat /boot/grub/grub.cfg | egrep subvol | head -n1
     linux    /pegaz/boot/vmlinuz-4.19.0-14-amd64
root=UUID=ea6ae51d-d9b0-4628-a8f3-3406e1dc59c6 ro rootflags=subvol=pegaz
rootflags=space_cache=v2 quiet



This one is iginored:

              rootflags=subvol=pegaz

and this one takes effect:

               rootflags=space_cache=v2

so default subvolume is mounted instead of "pegaz" subvolume.
This is severe and can change how system boots.


My workaround is to put whole rootflags in /etc/default/grub:


root@pegaz:~# egrep rootflags= /etc/default/grub
GRUB_CMDLINE_LINUX="rootflags=clear_cache,space_cache=v2,subvol=pegaz"


root@pegaz:~# egrep rootflags= /boot/grub/grub.cfg | head -n1

     linux    /pegaz/boot/vmlinuz-4.19.0-14-amd64
root=UUID=ea6ae51d-d9b0-4628-a8f3-3406e1dc59c6 ro rootflags=subvol=pegaz
rootflags=clear_cache,space_cache=v2,subvol=pegaz quiet



This is ignored:

              rootflags=subvol=pegaz

and this takes effect:


             rootflags=clear_cache,space_cache=v2,subvol=pegaz