Ckpt (http://pages.cs.wisc.edu/~zandy/ckpt/) was another user-space solution that worked quite
well for me until glibc & kernel changes bit-rotted it. Victor Zandy revised it a few times
to keep it alive, but it was originally a PhD research project and he moved on to other
things. It went down the LD_PRELOAD route that cryopid seems to be avoiding and I suspect
that might have made it more fragile.