I ran into a problem today upgrading my kernel which I had not encountered before and which required the help of a live slackware drive to fix.
My PC is over 8 years old and back then the way I found to set up dual booting was to have the vmlinuz kernels on the EFI partition itself. This requires mounting the EFI partition to copy over the files; I do not have the partition mounted by default.
This time round I found that after I had installed the kernel using slackpkg I could not mount the EFI drive. I was getting an error that vfat was an unknown type. I don't really understand why that should have happened (perhaps some kernel module has to be loaded)but in future I will make sure the EFI drive is mounted before upgrading the kernel. If I haven't upgraded my PC by then.

I've experienced this before, but with ext2 vs. ext4 file systems.

What happens is that since the EFI hasn't been mounted, the running kernel hasn't loaded the vfat module. Then when you "slackpkg upgrade," it removes the module tree from /lib/modules/{RUNNING KERNEL VERSION}. When you try to mount the EFI partition, the kernel can't find its own vfat module.

For everything to go smoothly, you must either A) mount your vfat partition (or any other file system of a type different from your main partition) before performing the upgrade, or B) re-install the kernel-modules package that corresponds to the version of the un-updated running kernel. (If you haven't rebooted yet, option B should allow you to go ahead and mount the vfat and proceed normally.)

EDIT:
Technically speaking, you don't have to mount the partition before upgrading the kernel--as long as the vfat module is loaded before you upgrade. (E.g., via modprobe.) In my case, I just include the vfat module in the initrd, then EFI is always available to mount, before or after the upgrade...

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The way to prevent this from happening next time is to include the vfat module in your initrd.

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Yeah, I've done that before.

I mount /boot/efi 'ro' on boot to make sure the vfat module is loaded, and then just flip it rw while it is updated.

For my custom kernels, I always build vfat in.

I was about to suggest again dracut (associated with GRUB of course) but I know, NIH syndrome et all. And we would miss all these "I can't reboot after a kernel upgrade" threads...

@GazL: no port of lilo or elilo for CRUX? What a shame!

Well, perhaps NAN syndrome? (Not absolutely necessary) I mean:

is not really rocket science, is it?

Or installpkg the new kernel instead of upgradepkg so current kernel modules files are still present in the hard drive

I do like rkelsen's approach.

No, no elilo/lilo in CRUXland. Initially I borrowed Slackware's elilo and mkinitrd to boot CRUX, but later moved away from that. I boot CRUX using the kernel's EFI_STUB direct from the EFI firmware boot menu, with no additional boot-manager at all. As for the initrds, CRUX doesn't officially support one, and that sort of thing is left to the user/admin to sort out ( There's a lot of that with CRUX! ).

There is a build of dracut in CRUX's "opt" package build collection, and I did try it, and it did indeed work, but I decided to write and use my own, driven by a simple makefile.

In contrast, my Slackware 15.0 install still uses elilo and Slackware's mkinitrd.


P.S. It's never been about NIH for me, it's an aversion to complexity.

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Amzingly, there are these two options of dracut:I guess you don't need that

Maybe I will try --uefi-stub some day if I am really bored...

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That is good to know.