Re: [gentoo-user] Installing BTRFS on MBR with OpenRC

[Jeremi Piotrowski]

On Thu, 6 Aug 2015, Peter Humphrey wrote:
> First, btrfs balance. I had no idea that was needed, so of course I didn't
> include it in my attempts. Could that be why, on booting, the kernel couldn't
> mount the file system?

I don't think that balancing an empty btrfs filesystem is necessary. It
should have no effect at this point and would not affect the kernel's
ability to mount the btrfs volume.

> Second, --xattrs on the tarball extraction. I haven't seen this recommended
> before, and I wonder what extra attributes are needed for btrfs.

This is part of the normal installation procedure and is not specific to
btrfs. See [1]. For all I know this has always been part of the
installation. 

> Third, why do you do your kernel compiling in /var/tmp/linux? It seems like
> extra work and I can't see a reason for it.

The kernel developers recommend to __never__ compile the kernel as root. 
You never know when something like `rm -rf /` might creep into the 
Makefile ;) The portage unpacked kernel sources belong to root:root so 
Rich's method compiles them in /var/tmp/linux which can be done as the 
local user.

> Finally, can I assume that your procedure would work just as well installing
> into, say, /dev/sd[ab]4?

Yep, but as stated by Rich there isn't much to a btrfs raid 1 install
aside from mkfs.btrfs, building btrfs support into the
kernel, the slightly different fstab entry, and using an initramfs (dracut
makes it easy).

I do recommend that you try it in a virtual machine first. With an
initramfs it worked out of the box for me but I wasn't able to get it to
work with just the kernel command line. 

[1]: https://wiki.gentoo.org/wiki/Handbook:AMD64/Full/Installation#Unpacking_the_stage_tarball