Computing notes 2026 part one

This document contains only my personal opinions and calls of judgement, and where any comment is made as to the quality of anybody's work, the comment is an opinion, in my judgement.

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2026 June

20260613Surprises when fixing some boot issues

So I had installed Ubuntu to run some tests on a small-PC style computer and then it failed to complete booting, stopping at the prompt for the decryption key of the / filesystem.

So I first tested the hardware (RAM, SSD self test as it was old and I had been messing with it a bit, but it all seemed good and anyhow it worked well if I booted from a USB stick the bootable deskptop version of Ubuntu.

Using the latter I looked at the install system and the first issue seemed to be that in /etc/default/grub the setting GRUB_ENABLE_CRYPTODISK=y was missing, even if the existing script prompted for the decryption password; so to be sure I (re)added that and re-generated the initial boot script for GRUB2, but the boot process still stopped at the prompt for the boot password.

A web search suggested that the initramfs image was missing some drivers (the hid related drivers). I had never considered this possibility because I has assumed that both the serial (PS/2 port) and USB keyboard drivers would be built-in the kernel. Well at least not for Ubuntu 24.

So I wanted to fix that with GRML 2026.04 but the I had further issues as it only booted in BIOS mode and not in UEFI mode and this meant it could not install GRUB2 properly. It turned out that the 2026.04 version of the GRML image does not come with a built-in partition table so UEFI implementations that will only boot from an ESP cannot boot it in UEFI mode.

This can be fixed by creating an ESP on the USB stick and mounting it, mounting the GRML image, copying from the mounted GRML image to the mounted ESP recursively. The resulting USB stick will only then boot as UEFI because it does not have the BIOS MBR. To make it bootable in the BIOS way follow the "Manual approach" section in this GRML wiki page.

After this I booted GRML in UEFI mode and chroot'ed into the system's / filesystem to first rebuilt the initramfs and then just to be I reinstalled GRUB2 but found that in addition to the usual /dev, /sys, /proc filesystems I had to bind-mount also /sys/class/firmware/efivars.

In summary I have learned a few new things:

• The drivers for USB keyboards are not necessarily built-in kernels for some popular distributions. I spent quite a bit of time looking for other causes because of a wrong assumption.
• Some UEFI implementations understanably can only boot from an explicitly partitioned device with an ESP.
• The GRML 2026.04 image does not have an ESP partition so it is not directly bootable in UEFI mode on some devices.
• It is easy to convert the contents of the GRML image to an ESP.
• When chroot'ing into an installed / from a live USB/CD/DVD image one should also bind-mount /sys/class/firmware/efivars for commands related to EFI.