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

[Peter Humphrey]

On Friday 31 July 2015 13:33:18 I wrote:
> On Friday 31 July 2015 06:44:54 Rich Freeman wrote:
> > As Neil already pointed out, if you're not using an initramfs you need
> > to put all your devices on this line if they're part of an array.  The
> > kernel will not scan to find the others.
>
> I didn't mention it the first time but I'd already tried
> device=/dev/sda3,device=/dev/sdb3 on the command line and it didn't help.
> I'd also tried the initramfs but that didn't help either. I'll try them
> again.

This time I tried "device=/dev/sda3,/dev/sdb3" in case that was the proper
syntax, but it made no discernible difference - the final message from the
kernel panic was the same "VFS: Unable to mount roofs on unknown-block(8,3)".

--->8

> > I believe that as long as dracut can find the btrfs utility it will
> > put it in the initramfs.

Indeed it did so for me (this was today when I ran
"dracut --kver 4.0.5-gentoo" again:

# lsinitrd -k 4.0.5-gentoo | grep btr
btrfs
-rwxr-xr-x   1 root     root          142 Jun 15 11:27 lib64/dracut/hooks/initqueue/timeout/10-btrfs_timeout.sh
-rw-r--r--   1 root     root          418 Apr 26 14:07 lib64/udev/rules.d/64-btrfs.rules
-rwxr-xr-x   1 root     root       427048 Jul 31 13:39 sbin/btrfs
-rwxr-xr-x   1 root     root       427048 Jul 31 13:39 sbin/btrfsck
-rwxr-xr-x   1 root     root       187384 Jul 31 13:39 sbin/btrfs-zero-log
-rwxr-xr-x   1 root     root         1196 Jul 30 08:50 sbin/fsck.btrfs

> > Otherwise there isn't much more to this

I've been thinking that for a few days now :)

> > I think these two issues are the only real problems you're having,
> > depending on which route you decide to take with the initramfs (which I
> > still recommend, but you could of course have separate grub lines to boot
> > with and without it if you want to experiment).

Yes, I'm playing with two grub entries, of which one tries devices= and the
other includes this line (is the syntax right? The file does exist):

initrd /boot/initramfs-4.0.5-gentoo.img

In the case of the initramfs the 8,3 in the kernel panic message becomes 8,19.
Is that a useful clue?

Another wobbler: as far as I can remember I haven't done anything about
compression, but could it have crept in somewhere?

And another: my dicky memory says that after booting SysRescCD to lay out the
new partitions and restore my rescue system, I booted the latter to do the
rest of the work, including mkfs.btrfs. Perhaps I should start again right
from the beginning but using SysRescCD's mkfs.btrfs. That'll be another day's
work.

-- 
Rgds
Peter