When adding a public key to /home/ubuntu/.ssh/authorized_keys, it appears the file was wiped empty because the disk was full.
Unfortunately the person I talked through this process logged out and we don't have any password to access this root volume.
Is there any way to recover from this situation?
I have checked adding user data on reboot, but this only seems to be available when the server is stopped. We obviosuly also can't mount the root disk anywhere else without loosing it.