Installing any Ubuntu desktop on to RAID 1

This applies to Ubuntu desktop 14.04 and later; plus any derivatives.

If you try to install Ubuntu desktop on to RAID, it will fail. The Ubiquity installer simply does no support RAID and will throw fatal errors no matter what you do. All hope is not lost, it is possible to jolly things along and have a working system. The basic steps are:

1. Set-up your RAID (if it does not already exist);
2. Add raid support to the live instance (mdadm);
3. Run Ubiquity without setting a bootloader; and
4. Chroot to your RAID, install support for it (mdadm again), finally install the bootloader to both physical drives (grub-install).

Rather than repeat everything, you can get all there steps in this answer, what I will detail is where I had to deviate from the instructions to make things work as I did it on Kubuntu 16.04 with a slightly different RAID 1 configuration.

Running Ubiquity: ubiquity -b kde_ui


With the RAID set-up, I had “/boot” off on its own partition. There was probably some good reason for that in the dim and distant past, but for the life of me I have no idea what it was. In my case, this was “/dev/md0” and my root partition was “/dev/md1“. I had to mount “/boot” in before doing the actual chroot or the grub-install steps would have failed. After “mount /dev/md1 /mnt” I then ran “mount /dev/md0 /mnt/boot” and that was that.

It might look a bit daunting, but if you’ve managed to set-up RAID then you probably have the technical chops to cope. The main irritation is that the Ubuntu Live CDs have no support for RAID and perform no checks prior to letting try to install. Coupled with the fact that the error is simply “Executing 'grub-install /dev/sda failed. This is a fatal error.” you can waste a lot of time trying to figure out what mistake you’ve made.

I really wish Canonical would either provide RAID support for the Live image; maybe optionally install “mdadm” in to Live when Ubiquity runs (as well as making sure it gets pushed into the install).