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

[Peter Humphrey]

On Friday 31 July 2015 13:53:42 Dale wrote:
> 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.

--->8

> 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.

That could well be it, Dale. I tried both my currently installed kernels, 
3.18.16 and 4.0.5, but of course they're both later than 3.18.7. I'd still 
like to get this working, so I'll install an earlier kernel and try that - 
when I've had a bit of a rest!

Thanks for the clue.

-- 
Rgds
Peter