Btrfs limitations in the Debian installer 7.0 beta4 release
Forwarding this interesting message re d-i feedback and using BTRFS in
the installer from -devel.
----- Forwarded message from Aaron Toponce <aaron.toponce@gmail.com> -----
From: Aaron Toponce <aaron.toponce@gmail.com>
Subject: Btrfs limitations in the Debian installer 7.0 beta4 release
Date: Thu, 13 Dec 2012 09:43:20 -0700
To: debian-devel@lists.debian.org
Recently, I decided to put down a Btrfs root on my workstation using the
latest release of the installer. I found that given my hardware
configuration, this is not possible, and would require using another
installer or debootstrap the installation, which is far from ideal.
I have two 250 GB drives I would like to put into a RAID-1 mirror. I want
Btrfs to handle the RAID, rather than mdadm. It appears that this is not
possible in the installer, as when you are at the partitioning screen, it
forces you to decide which partition gets mounted to root.
Instead, I'll pull up tty2, and manually build the array. Suppose they are
identified as /dev/sda and /dev/sdb. I would like to partition the drives,
such that /dev/sda1 and /dev/sdb1 make up the root Btrfs filesystem, and
/dev/sda2 and /dev/sdb2 make up a ZFS /home.
After partitioning the devices, I run the following command to create the
Btrfs RAID:
# mkfs.btrfs -d raid1 -m raid1 /dev/sda1 /dev/sdb1
# mount /dev/sda1 /target/
Now, I would prefer to have the root into a subvolume. So, I run the
following command:
# cd /target/
# btrfs subvolume create root
# cd
# umount /target/
# mount -t btrfs -o defaults,subvol=root /dev/sda1 /target/
Recognize that I am effectively mounting /dev/sda1/root (if such a device
actually existed) to /target/, and not /dev/sda1. However, the partitioning
utility will not allow me to modify the mount options when specifying which
subvolume should be mounted to /.
So, if I specify /dev/sda1 to be /, the debian installer will "umount
/target/" and "mount /dev/sda1 /target/" which is not what I want.
Further, asside from pulling up a terminal in the installer, there is now
way in the partitioning utility to setup Btrfs volumes using multiple
devices. You must set that up in tty2 or tty3. (As a tangent gripe, the
partitioner will also not allow you to setup an encrypted partition. You
must do encrypted volumes with LVM. You can defeat this by again going to a
TTY.)
Doing a GRUB install on both /dev/sda and /dev/sdb is not a problem, and I
can configure GRUB to assemble the Btrfs volume, and I can make the
necessary changes to notify the kernel where the root filesystem is.
However, all of these require stepping out of the Debian installer, and
using another vendor's install, such as Ubuntu or Fedora, to bootstrap it.
Again, far from ideal.
It would be nice if the partitioning utility allowed the administrator to
specify mount options (asside from checkboxes with 'noatime', 'relatime',
etc). This way, I could tell the installer to mount the subvolume as root,
and not the partition.
I can file a feature request, if needed.
Thanks,
--
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----- End forwarded message -----
--
I pledge not to post to any systemd-related thread on -devel until
(at least) 2013.
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