Installer crash on RAID system

[Paul Crawford]

Trying to install 18.04.2 on to existing assembled RAID system. Got to the grub installation phase and it then generated an error dialogue window saing it could not install to /dev/sda /dev/sdb (the usual for RAID) but none of the alternatives in the radio button choice actually allowed a continuation.

If it could not do the grub step then the alternatives ought to at least work!

$ lsb_release -rd
Description: Ubuntu 18.04.2 LTS
Release: 18.04

$ apt-cache policy ubiquity
ubiquity:
  Installed: 18.04.14.12
  Candidate: 18.04.14.12
  Version table:
 *** 18.04.14.12 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     18.04.14 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.12
ProcVersionSignature: Ubuntu 4.18.0-15.16~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-15-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CasperVersion: 1.394
Date: Wed Jun 12 21:22:17 2019
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd quiet splash ---
LiveMediaBuild: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)