Boot – Fix Ubuntu 18.04.2 Boot Stuck on Purple Screen After Updates

18.04bootfreezegrub2updates

Summary of Issue

Last Friday, I installed updates to Ubuntu 18.04 with sudo apt-get update && sudo apt-get upgrade. Some of these updates required a restart. Upon restart, after GRUB, boot got stuck on a purple screen before the Ubuntu logo/login. I can't access the terminal at this step through Ctrl + Alt + F7/T/F1/F2 methods. Recovery mode does not work, and gets stuck at Loading initial ramdisk...

Attempts to Resolve

As stated above, recovery mode did not work.

  1. Attempted to use Boot Repair, this ran successfully but did not resolve the problem. Output from this attempt here.

  2. Next, I backed up some files then attempted a fresh install of 18.04.2. This worked, but as soon as I grabbed the ~400 MB of updates for this clean install, I encountered the same problem as before. I tried using both the Software Updater, and terminal. I've got no idea what update is breaking, here's a full log of updates run.

  3. Saw what may be a related issue here: Ubuntu freeze on boot purple screen. Seeing that this user seemed to have an issue with kernel updates, I excluded kernel updates from running and tried again, still the same result as before.

So at this point, I'm at a loss as to how to proceed. I'm hoping I can get some help on this thread. Otherwise, I may need to downgrade to 16.04 or upgrade to 19.04.

EDIT 1

Looks like this bug's already been reported to Canonical. Appears that it could be related to recent Intel microcode updates or an acpi issue.

EDIT 2

Intel microcode updates on ASUS causing kernel to get stuck has been identified as the crux of the issue. Confirmed temporary workaround to get machines bootable is in the accepted answer below.

A video from YouTube regarding this problem and the documented workaround.

EDIT 3

As of 09/03/2019, I've installed the most recent BIOS update from ASUS (from within Windows 10) and can confirm that this enables me to boot normally into Ubuntu without the need for the dis_ucode_ldr option in GRUB. I would recommend this as a more sustainable, definitive fix for the problem than using the workaround at this point.

Best Answer

Well I also have a Asus ZenBook UX433FA doing this issue, I was running 18.10 and did apt-get upgrade last night and broke the system.

I've since used this method livecd recovery to upgrade to 19.04 still no luck with booting. Have multiple kernels installed none of which will get past the "loading initial ramdisk". While using the above i installed kernel v5.1 with ukuu no luck either and threw errors about dkms for nvidia driver incompatible with kernel version.

Edit DMESG log

Managed to get the dmesg from a partial boot here

boot-repair log info here occasionally it will boot with errors, unsure of what info or how to gather info on these occasions though to help with debug.

Just a side note windows hadn't been loaded for about a month prior to this. I know this should probably be a comment but I don't have enough credit.

Edit 2

For anyone having a similar problem, try booting with microcode updates off: add dis_ucode_ldr to the kernel command line (from GRUB if you cannot boot) can confirm this allows for boot.

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