Re: [gentoo-user] Can't boot btrfs

[Dale]

Peter Humphrey wrote:
> Hello list,
>
> I've created a new btrfs volume on SSDs, complete with a lot of subvolumes
> corresponding to the old lvm2 logical volumes. I took the opportunity of
> removing a couple of old partitions, so I now have this:
>
> /dev/sd[ab]1 form /dev/md1 as /boot,
> /dev/sd[ab]2 are my rescue system: sda2 is its root, sdb2 is its portage tree,
> /dev/sd[ab]3 is the btrfs file system.
>
> I can boot my rescue system with no problems, but not the main system - I get
> a kernel panic with "BTRFS: failed to read the system array on sda3". I'm
> writing this after chroot, su - prh, startx.
>
> Both in the main and rescue systems I have this:
> $ grep -i btrfs /usr/src/linux/.config
> CONFIG_BTRFS_FS=y
> CONFIG_BTRFS_FS_POSIX_ACL=y
> # CONFIG_BTRFS_FS_CHECK_INTEGRITY is not set
> # CONFIG_BTRFS_FS_RUN_SANITY_TESTS is not set
> # CONFIG_BTRFS_DEBUG is not set
> # CONFIG_BTRFS_ASSERT is not set
>
> The relevant grub.cfg entries (I've moved to grub-2) are:
>
> menuentry 'Gentoo Linux 4.0.5, no network' {
>         linux /boot/kernel-x86_64-4.0.5-gentoo root=/dev/sda3 softlevel=nonet
> net.ifnames=0 irqpoll
> }
> menuentry 'Rescue System 4.0.5' {
>         linux /boot/kernel-x86_64-4.0.5-gentoo-rescue root=/dev/sda2
> net.ifnames=0 irqpoll
> }
>
> Something seemed to be wrong in the kernel setup, so to test that I compiled
> the main kernel with the .config from the rescue system. Same result.
>
> Another test: I wondered whether, somehow, the btrfs volume included the name
> of the mount point where it had been created, and would only allow itself to
> be mounted there. Not so: moving its mount point in the rescue system didn't
> prevent it from being mounted. I didn't expect it would, since the kernel
> panic occurs long before fstab is read.
>
> The other thing I've tried is to build an initramfs with dracut. I tried to
> include its btrfs module but it refused because it couldn't find a command
> btrfs. So I recompiled the kernel with btrfs as a module and added
> 'filesystems+="btrfs" ' into dracut.conf. Still no success.
>
> After a few days of floundering around, copious googling and getting splinters
> under my fingernails I'm out of ideas. Can anyone see what else I can try? I
> created the btrfs with "mkfs.btrfs -m raid1 -d raid1 --label GENTOO /dev/sda3
> /dev/sdb3". I've done that twice, with all the subvolume creation and backup
> recovery, the second time with --force.
>


This may not be related but thought I would mention.  For some reason,
my system will not boot a kernel newer than 3.18.7.  I use
gentoo-sources and generally use make oldconfig.  I have also tried the
new 4.0 kernels as well.  They try to boot but don't make it past the
kernel trying to do its thing.  I don't reboot often so I have not had
the chance to figure out exactly why this is happening.  Recently I had
to start using that pesky init thingy but I don't think that is causing
the problem.   I get a error/panic and then it says it is going to
reboot in 10 seconds.  By the time I figure out where the failure might
be, it reboots itself. 

I thought I would mention just in the rare event you are running into
the same issue I am.  Just a thought.  If you know this isn't the
problem, just ignore and carry on. 

Dale

:-)  :-)