The util you're looking for is sysctl (Or a system-call by the
same name). However, as far as I know this isn't quite fully
implemented in Linux as of yet (I just saw it on a "wishlist"
for 2.2 kernels). Certainly I haven't been able to find
anything meaningful on sysctl in Linux, so perhaps that post
you was referring to was abotu the *BSD's which I seem to
remember use sysctl rather heavily. Ofcourse there's the option
to choose whether or not to compile sysctl in to the kernel
at least on 2.1.37; if anybody knows for sure if working
sysctl utils can be had anywhere, drop a line.
However, on the grand scale, I don't think sysctl would do it- Linux (Ok, again, at least in 2.1.37) comes with all defaults compiled to 1024fd's, and changing that would require at least increasing _FD_SETSIZE, NR_FILE and NR_OPEN. You'd have to change these in the kernel headers and recompile everything to get any changes of it working anyway.
On the grand scale, though, I somehow doubt this is your problem - running out of file descriptors rarely results in kernel crashes.