I copied my hard drive's kernel and modules to a flash drive. It crashes on boot, reporting:It gave a similar error when I used the package kernel.

I need a bit more info. How exactly are you using the flash drive in relation to '/'? Are you mounting it to /boot? /lib? It can't be both.

I try to boot from the flash drive: it's /. It passes e2fsck; running diff on the kernel and modules, comparing them to those on the hard drive, find no differences.

it may be that some of the APM type modules were not loaded properly (cpu slept, some module not loaded was supposed to wake it not present, etc)

your main system might use an "initrd" to load modules during boot time (ugh, rather have a kernel with all the stuff my pc does compiled in). it could be you have some support in kernel but some essential support "compiled as module". having modules isn't enough. linux can't load them until it mounts root which in your case appears to be too late. (that's what initrd is for)

i think you need to learn more about making an "OS DISK". you can't just copy a few things and expect it all to work.

or try a different OS/kernel. there are some where doing a copy like that would work.

all depends on what you like doing and how you like doing it. but rtfm