After updating Lubuntu 22.04.1 lts to 24.04.1 lts, the cryptsetup prompt to enter the password to decrypt the root partition no longer appears on an external monitor attached to the laptop where Lubuntu is installed. Rather, it only appears on the built-in display. In Lubuntu 22.04, the prompt always appeared on both displays, whether the laptop lid was open or not. Now on 24.04 it does not show up at all on the external monitor regardless of the state of the lid. Once the correct password is entered, the external display works as desired and configured, showing the user login prompt. I can’t figure out how to tell cryptsetup that there are multiple displays and to please use them both to ask me to decrypt root. I never encountered this issue in Lubuntu 22.04
I can’t help, and my understanding is far too limited to be exact sorry… however
Your system isn’t fully functional as its still early in the boot process when you enter the encryption key, thus your hardware and its firmware have an influence on how it operates. I’ve used laptops where I could control which display showed (ie. internal and/or external) grub & the decryption prompt via firmware (BIOS) settings and/or fn-keys on the device, and other laptops where I had no control. I’ve also noted using the exact same software, different devices operating differently at this early stage (due to their different hardware & firmware with identical software configurations).
Ubuntu 24.04 (and I consider Lubuntu a Ubuntu system, thus my wording) is two years newer in regards software (kernel stack can differ as I don’t know if you were using GA or HWE kernels, with Lubuntu this default is set by what install media you use) thus the software stack component has changed, which influences how your machine operates… but I’m not sure how much control you have, and do believe what control you do have will very much be specific to your hardware given the OS isn’t fully operational yet.
I can’t help sorry, but I am warning I suspect you’ll find your answer may not perfectly match what works for others using different hardware, as I suspect your issue is hardware/firmware specific.
Thank you,guiverc, for the observations.
Regarding “…if you were using GA or HWE kernels, with Lubuntu this default is set by what install media you use”, I was running the 24.04 upgrade from the 22.04 installation Software Updater, so there was no external media being used. This was the 22.04 install that displayed cryptsetup prompts on both monitors. Does this clarify the GA or HWE kernel issue?
Regarding “Your system isn’t fully functional as its still early in the boot process when you enter the encryption key”, the 22.04 cryptsetup is running in a known 2-monitor environment so is the process or configuration file that establishes that 2-monitor environment now skipped or mis-configured when 24.04 runs cryptsetup? Could that be corrected by resequencing or reconfiguring an underlaying boot process?
Regarding “… I consider Lubuntu a Ubuntu system”, is it appropriate to ask about this behavior in Ubuntu discourse? I would expect to possibly get some pushback about “boundaries”.
Lubuntu 22.04 & 22.04.1 LTS media installs using the GA kernel stack, where as Lubuntu 22.04.2 thru 22.04.5 media will install with the HWE kernel stack. When you release-upgrade to later releases (ie. 24.04), your default stack remains the same; being set by your install media.
If you installed your system with a stack (say HWE) at 22.04, and then added the other stack (so your system has installed & offers at grub both GA & HWE choices), when you release-upgrade to 24.04 you’ll remain with both kernel stack options. The GA kernel for 24.04 is 6.8, where the next HWE kernel is 6.11; only available now if you’re using edge-proposed, or
linux-image-generic-hwe-24.04-edge | 6.11.0-12.13~24.04.1 | noble-proposed | amd64, arm64, armhf, ppc64el, s390x
but that kernel will advance until it’s available for normal users; ie. 24.04 is still somewhat new & hasn’t yet got its first HWE kernel being 6.11 from 24.10; but it’s visible & coming.
Ubuntu Forums is now using the Ubuntu Community Hub or Ubuntu’s discourse, and Ubuntu Forums allows questions about any official Ubuntu flavor including Lubuntu. I wouldn’t expect pushback if you asked questions there (I’m a mod there too if you look; and not the only person here who can say that either). We do appreciate it when people don’t ask a question at multiple support sites at the same time! but try one site, and only move/try seeking help at other sites if they didn’t get help at their first site (we have no issues with that approach).
Sorry I can’t provide help (or even opinion) on that question.