encrypted passphrase prompt not shown on external display

[Brian Murray]

I upgraded my laptop with an external display from 17.04 to 17.10 and now the prompt for entering my encrypted passphrase only appears on the laptop's internal display. I didn't realize this and presumably the laptop was stuck waiting for my passphrase when I went to bed and sometime in the middle of the night the battery ran out and I was awoken by a loud beep from the laptop. That was rather unpleasant but not terribly relevant to the bug.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: plymouth 0.9.2-3ubuntu17
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
ApportVersion: 2.20.7-0ubuntu3
Architecture: amd64
BootLog:

CurrentDesktop: ubuntu:GNOME
Date: Mon Oct 16 10:06:02 2017
DefaultPlymouth: /usr/share/plymouth/themes/ubuntu-logo/ubuntu-logo.plymouth
InstallationDate: Installed on 2014-03-06 (1319 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140306)
MachineType: LENOVO 0831CTO
ProcCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-16-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M vt.handoff=7
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-16-generic root=/dev/mapper/ubuntu--vg-root ro quiet splash crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M vt.handoff=7
SourcePackage: plymouth
TextPlymouth: /usr/share/plymouth/themes/ubuntu-text/ubuntu-text.plymouth
UpgradeStatus: Upgraded to artful on 2017-10-15 (1 days ago)
dmi.bios.date: 09/15/2010
dmi.bios.vendor: LENOVO
dmi.bios.version: 6QET53WW (1.23 )
dmi.board.name: 0831CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr6QET53WW(1.23):bd09/15/2010:svnLENOVO:pn0831CTO:pvrThinkPadX201Tablet:rvnLENOVO:rn0831CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.family: ThinkPad X201 Tablet
dmi.product.name: 0831CTO
dmi.product.version: ThinkPad X201 Tablet
dmi.sys.vendor: LENOVO

[Steve Langasek (vorlon)]

I see the same behavior here.

[Steve Langasek (vorlon)]

I suspect this is a kernel bug, and the same as bug #1724911.

[Steve Langasek (vorlon)]

I have confirmed that the upstream kernel that fixes bug #1724911, 4.14rc5, also fixes the problem of plymouth not displaying on the external monitor; so marking this as a duplicate.