This is just a reminder for my future self on how to set up a hetzner dedicated server with btrfs in rescue mode. I think the examples they provided were a bit confusing, at least to me.

We needed a filesystem without the notion of inodes since we were dealing with millions of super teeny-tiny files and ext4 wasn’t suitable for this without lots of modifications since we were also using kubernetes with a managed storage controller and couldn’t adapt the ext4 formatting options.

let’s get to it.

  • boot into rescue mode
  • create a file called installimage.conf and paste this one in there:
# Hetzner Online GmbH - installimage
# This file contains the configuration used to install this
# system via installimage script. Comments have been removed.
# More information about the installimage script and
# automatic installations can be found in our wiki:

DRIVE1 /dev/sda
DRIVE2 /dev/sdb
HOSTNAME your-hostname
PART btrfs.1    btrfs       all
SUBVOL btrfs.1  @           /
IMAGE /root/.oldroot/nfs/install/../images/Ubuntu-2004-focal-64-minimal.tar.gz

you may want to edit the HOSTNAME part and also check if the IMAGE is still current and the right one.

you can start the installation with

installimage -c installimage.conf

the example above will create a software raid 1 with two drives and use btrfs as the root volume, creating one subvolume located at /.