That's because rootfs has systemd-backlight@.service to restore/save the brightness value. Probably a good idea to do the same for initramfs.
** Also affects: initramfs-tools (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1738490 Title: current boot config dims screen during initramfs Status in initramfs-tools package in Ubuntu: New Status in linux package in Ubuntu: Incomplete Bug description: This is a weird one. Shortly after moving to 17.10, my laptop has started dimming its internal screen to minimum brightness at the start of initramfs execution. shortly thereafter it restores it to normal brightness, but that only happens *after* typing in encrypted filesystem passwords, so the password dialogues are practically invisible. Not sure why its doing this, but whatever's restoring the brightness should do it before prompting for filesystem mounting so these prompts are actually visible. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: linux-generic 4.13.0.19.20 ProcVersionSignature: Ubuntu 4.13.0-19.22-generic 4.13.13 Uname: Linux 4.13.0-19-generic x86_64 NonfreeKernelModules: zfs zunicode zavl zcommon znvpair ApportVersion: 2.20.7-0ubuntu3.6 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: tessa 17026 F.... pulseaudio /dev/snd/controlC1: tessa 17026 F.... pulseaudio CurrentDesktop: GNOME Date: Fri Dec 15 13:44:02 2017 InstallationDate: Installed on 2016-07-08 (524 days ago) InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1) MachineType: Apple Inc. MacBookPro11,4 ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-19-generic.efi.signed root=ZFS=rpool/root ro quiet splash vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-4.13.0-19-generic N/A linux-backports-modules-4.13.0-19-generic N/A linux-firmware 1.169.1 SourcePackage: linux UpgradeStatus: Upgraded to artful on 2017-10-19 (57 days ago) dmi.bios.date: 08/08/2017 dmi.bios.vendor: Apple Inc. dmi.bios.version: MBP114.88Z.0177.B00.1708080033 dmi.board.name: Mac-06F11FD93F0323C5 dmi.board.vendor: Apple Inc. dmi.board.version: MacBookPro11,4 dmi.chassis.type: 9 dmi.chassis.vendor: Apple Inc. dmi.chassis.version: Mac-06F11FD93F0323C5 dmi.modalias: dmi:bvnAppleInc.:bvrMBP114.88Z.0177.B00.1708080033:bd08/08/2017:svnAppleInc.:pnMacBookPro11,4:pvr1.0:rvnAppleInc.:rnMac-06F11FD93F0323C5:rvrMacBookPro11,4:cvnAppleInc.:ct9:cvrMac-06F11FD93F0323C5: dmi.product.family: MacBook Pro dmi.product.name: MacBookPro11,4 dmi.product.version: 1.0 dmi.sys.vendor: Apple Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/initramfs-tools/+bug/1738490/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp