Can't boot with degraded RAID 1

[Eero]

I just made a fresh install from ubuntu-16.04.2-server-amd64.iso, updated all packages, and tested to boot without one disk. It failed.

See the attached screenshot for error messages.

This is probably the same bug as https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=859691

Workaround:
mdadm --run /dev/md0
[CTRL+D] (to exit initramfs shell)

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: mdadm 3.3-2ubuntu7.2
ProcVersionSignature: Ubuntu 4.4.0-72.93-generic 4.4.49
Uname: Linux 4.4.0-72-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
Date: Thu Apr 6 15:18:22 2017
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-04-06 (0 days ago)
InstallationMedia: Ubuntu-Server 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.8)
Lsusb:
 Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MDadmExamine.dev.sda: Error: command ['/sbin/mdadm', '-E', '/dev/sda'] failed with exit code 1: mdadm: cannot open /dev/sda: Permission denied
MDadmExamine.dev.sda1: Error: command ['/sbin/mdadm', '-E', '/dev/sda1'] failed with exit code 1: mdadm: cannot open /dev/sda1: Permission denied
MDadmExamine.dev.sdb: Error: command ['/sbin/mdadm', '-E', '/dev/sdb'] failed with exit code 1: mdadm: cannot open /dev/sdb: Permission denied
MDadmExamine.dev.sdb1: Error: command ['/sbin/mdadm', '-E', '/dev/sdb1'] failed with exit code 1: mdadm: cannot open /dev/sdb1: Permission denied
MachineType: innotek GmbH VirtualBox
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-72-generic root=/dev/mapper/hostname--vg-root ro
ProcMDstat:
 Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
 md0 : active raid1 sdb1[2] sda1[0]
       8382464 blocks super 1.2 [2/2] [UU]

 unused devices: <none>
SourcePackage: mdadm
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH
etc.blkid.tab: Error: [Errno 2] No such file or directory: '/etc/blkid.tab'

[Eero (eero+launchpad)]

Adding a screenshot for the RAID configuration I used during the installation. First I created a RAID manually. Then I used the guided partitioning to set up an encrypted LVM.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.