what's "sure kill" when talking about NFS mount option?

Question

In the following link

http://www.faqs.org/docs/Linux-HOWTO/NFS-HOWTO.html

It said a process is not killable except by a "sure kill", but what's sure kill?

hard (NFS client mount option)

The program accessing a file on a NFS mounted file system will hang when the server crashes. The process cannot be interrupted or killed (except by a "sure kill") unless you also specify intr. When the NFS server is back online the program will continue undisturbed from where it was. We recommend using hard,intr on all NFS mounted file systems.

Answer 1

I think it means kill -9, though please note that you are reading a quite old howto (as most other TLDP howtos, I think) from 2002 year, and regarding NFS mount options hard,intr are already default and

The intr / nointr mount option is deprecated after kernel 2.6.25. Only SIGKILL can interrupt a pending NFS operation on these kernels, and if specified, this mount option is ignored to provide backwards compatibility with older kernels.