There are 2 NFS server implementations under Linux. One is the user-space NFS server. It was originally developed by Mark Shand, Donald J. Becker, Rick Sladkey, Orest Zborowski and Fred N. van Kempen. It has been maintained and improved by Olaf Kirch. At the same time, Olaf Kirch also was working on the kernel-space NFS server implementation for Linux.