Imagine you decided to go with modular kernel. You comment out 'device random' in your kernel-config and place 'random_load="YES"' in /boot/loader.conf. When you reboot and don't rebuild the kernel first, you have your machine unbootable - at least in case you previously had acpi in your kernel and acpi doesn't work without OS supplied dsdt (as in my case) or you need acpi as a module or any other module.
The way out is to boot from install CDROM, have fixit floppy, mount the old root and remove the random.ko module. Which is pretty inconvenient, when you don't have the medias handy.
The problem is that I can't ask loader not to load some module. It doesn't understand 'unset XX_load'. It doesn't work to say 'set XX_load="NO"' either. The only way I found to make it not load the modules is to 'load /boot/kernel/kernel;set module_path="";boot'. Unfortunately it doesn't help me either because I need to load special acpi_dsdt.aml which isn't then loaded either.
The fix could be to be able to say 'unset XX_load' or make 'set XX_load="NO"' work. The other fix (probably more difficult to do) would be to make all modules loading/linking fail when they're statically compiled in.
I'm working on replacing the present loader.conf support code with something that would let you do just that. Recent panics on current have stalled this work, though.
At any rate, this should work:
(enter loader, interrupt autoboot) unload disable-module random boot
MMMmmmmm. Let me try that... Yep, it works. And it's documented in loader.4th(8) too.
Now, I'll be the first to agree with you that the man pages that talk about boot are a maze. loader.4th(8) is mentioned in loader.conf(5), which is but a SEE ALSO of loader(8), which is referred to in boot(8).
The command doesn't appear on "?", though. *That* is a problem. I swear I was overloading "?" to display the enhanced commands once loader.4th was, well, loaded, but it seems that isn't the case.
--
Daniel C. Sobral
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