The procedure to build a kernel varies quite a bit from one release of HP-UX to another. Here is a
link to one of the procedures. I do not recommend copying /stand/system from one system to the next. Note that the procedure documented in that link does not trust /stand/system even on the box it was created on. The HP procedure recreates the system file each time a kernel is built. Also, depending on what you want to change, you may not need to rebuild the kernel. Again, stuff that is dynamicly reconfigurable also changes from release to release. You really need to look up the procedures for your HP-UX release and follow those. If the boxes are absolutely identical, copying /stand/vmunix over might work. But that is dangerous and could result in an unbootable system if anything goes wrong.