CoreOS on Hetzner w/hardware RADI1

The existing docs when attempting to install CoreOS on Hetzner are a bit incomplete. This caused a bit of frustration for me so I am putting this doc together in hopes that it will help someone else.

Pre-requisites

After ordering your server you will need to log into the Hetzner server console

Add a public key

Select Key Management
Select New Key
Give it a name and paste your public key into the key data field
Select Add Key

Rescue Mode

Select Servers
Select your server
Select Rescue
For the OS, select Linux. Select the appropriate Architecture and the Public key you added in the step above.
Select Activate rescue system
Select Rescue
Select Execute a automatic hardware reset then click Send

You may need to wait 30s to a few minutes before the server boots into rescue mode.

Configure your RAID

Hetzner should have installed both SAS drives with an Adaptec controller to /dev/sg0 and /dev/sg1 respectively. You can inspect these using smartctl for more details.

Build the RAID1 by using the following commands

arcconf CREATE 1 LOGICALDRIVE MAX 1 0 0 0 1 noprompt

Check to see if the drives are recognized

arcconf GETCONFIG 1 PD

Ensure any metadata is cleared

arcconf TASK START 1 DEVICE 0 0 CLEAR

More info on creating a RAID on Hetzner can be found here

CoreOS

Ensure your private key is being forwarded and SSH to the server as root. You should enter a rescue console running Debian.

Now run

wget https://raw.githubusercontent.com/coreos/init/master/bin/coreos-install

Create a cloud-config file which will bootstrap the server. Then run

./coreos-install -d /dev/sda -C stable -c cloud-config

After a few minutes CoreOS will be installed to /dev/sda. Log back into the console and run another Execute a automatic hardware reset. Alternatively, run reboot from the rescue console.

When the system comes back up your first node in your CoreOS cluster should be available.