Kubuntu 26.04.1 LTS install encrypted manual partition boot broken

[AspiringLinuxChampion]

Hi,

First I'm fairly new to Linux so bear with me. If someone could help me with this issue I would really appreciate it. I installed the Kubuntu 26.04.1 LTS to my desktop PC using the encrypted manual partition option in the installer. The installer ran it's course but now the boot seems to be broken, Kubuntu won't load and instead I always end up in the Grub 2.14 shell screen. I've tried it dozens of times and results are consistent.

Here are the installation options I used:

• Full installation with third party software
• Partition nvme0n1p1: 1024MB fat32 mount point "boot/efi" with "boot, esp" flags, unencrypted
• Partition nvme0n1p2: 1.8TB ext4 mount point "/" with no flag, encrypted

Using the Kubuntu USBs live desktop, after few days of research I managed to determine a few things. First the LUKS2 encrypted ext4 partition was created properly and I could open it with the passphrase. Second after mounting the unencrypted ext4 drive and examining the contents, the Kubuntu installation seemed to have been completed successfully too. I think I found all the basic directories and files, also those that to my understanding are needed for booting, listed below (directories marked [directory]).

/boot/: initrd.img, initrd.img.old, initrd.img-7.0.0-30-generic, vmlinuz, vmlinuz.old, vmlinuz-7.0.0-30-generic, mt86+ia32, mt86x64, System.map-7.0.0-30-generic, config-7.0.0-30-generic, [efi], [grub]
/boot/efi/EFI/BOOT/: BOOTX64.csv, fbx64.efi, mmx64.efi
/boot/efi/EFI/ubuntu/: BOOTX64.csv, grub.cfg, grubx64.efi, mmx64.efi, shimx64.efi
/boot/grub/: gfxblacklist.txt, grub.cfg, grubenv, locale.pf2, [fonts], [locale], [x86_64-efi]

I then found from the internet a few posts describing a similar sounding issue, all the way from Ubuntu 24.04. Some of these posts had answers that stated this was a Ubuntu related issue, some stated it was a Calamares installer related issue. Some posters seemed to have been able to fix the issue so I tried to replicate these steps.

This post describes a similar setup and issue. One reply states that the Ubuntu is missing LUKS2 modules, other that Ubuntu does not support encrypted /boot partitions at all and that a separate unencrypted /boot partition is needed.

Kubuntu 25.04 beta: Installing with an encrypted root filesystem results in a non-booting system
https://bugs.launchpad.net/ubuntu/+s...s/+bug/2105924

I checked my Kubuntu install and in /boot/grub/x86_64-efi/ I did find luks.mod & luks2.mod so I think my installation is not missing the LUKS2 modules? That latter reply regarding Ubuntu not supporting encrypted /boot partition is interesting and something I have seen on other threads too though.

This post describes an issue where the encrypted installation's etc/crypttab entry is missing "luks" at the end (luks-<uuid> UUID=<uuid> none). The user managed to fix the issue by changing the entry to include this text (luks-<uuid> UUID=<uuid> none luks).

[Bug 2172138] [NEW] Kubuntu 26.04.1 encrypted installation fails to boot; adding luks to crypttab fixes it
https://mail-archive.com/ubuntu-bugs...sg6326786.html

However I checked my etc/crypttab entry and it seems the entry already contains the "luks" text (luks-<uuid> UUID=<uuid> none luks) so I guess this is not my issue?

There are a few more posts describing a similar Ubuntu/Kubuntu FDE installation issue but these are for Windows dual boot systems. I did check the proposed fixes (there are a few KMDTech videos too) but they seem to involve playing with the dual boot properties so probably not applicable here.

One poster claims (I can't find this post right now unfortunately) to have managed to fix the issue by installing Kubuntu two times in a row - creating the boot/efi and encrypted Kubuntu partition with the manual partition option in the first pass, and then running the installer again simply overwriting the previous partition with a new installation. I haven't tried this yet as it obviously will overwrite everything.

At this point I'm not sure what to do. Should I try to fix the existing installation somehow, try the above reinstallation trick or purge the existing partitions and create new ones with the aforementioned additional unencrypted /boot partition? It feels odd to me that the official Kubuntu installer would allow me to create an encrypted system partition in the first place, if the feature is not supposed to work. So I still assume something went wrong with my installation. This would imply that I can either fix it or at least do a reinstall successfully. Any insights on this are most welcome, I'd really want to use the encryption for my system.

[claydoh]

Since you are only using a single / partition for the OS, what is wrong with just using the Encrypt checkbox in the installer?

Basically, you are missing the separate partition mounted as /boot (no flags) on top of the EFI and the encrypted root ( "/").
The checkbox does that for you.