Figure 3: NFS and POSIX (view as client)
As a POSIX program package, NFS depends on POSIX and utilizes the following POSIX functionality:
- The NFS commands are entered in the POSIX shell.
- Among other things, remote file system requests are processed in the POSIX subsystem.
For example, a file system request is first passed to the POSIX subsystem component VFS (Virtual File System). On the basis of the file system type, this recognizes whether a local or remote file system is to be processed:
If a local file system is to be processed, the request is dealt with by way of the POSIX component UFS (UNIX File System), the POSIX disk driver and the BS2000 component PPAM (Privileged Primary Access Method).
When a remote resource is to be processed, the request is handled through NFS. Communication with the remote computer is via RPCs (Remote Procedure Calls) and Kernel TLI (Transport Layer Interface) and the BS2000 component BCAM.