What is NFS server?

NFS word belongs to "Network File System". NFS allows to access files on server from network users which stored on computers of different types.NFS allow to access files by using Virtual File System (VFS) that runs on top of TCP/IP. With NFS, computers connected to a network as a client while accessing remote files, and as servers while providing remote users access to local shared files. With NFS we can mount all or a portion of a file system which will allow client to access partition or specific file/directory which we defined in NFS mount point for specific user or network.
Also refer following blog to collect more information http://theperfectarts.com/

How to check run level on Linux Server?

To check run level run "who -r" on shell it will show you current run level set on your server.

root@Gunjan [~]# who -r
run-level 3 2009-01-07 21:19 last=S
Also refer following blog to collect more information http://theperfectarts.com/

What is process ID zero and process ID one?

Process ID zero

All idle task has process ID zero and never exits.

Process ID one

The init process having process ID 1, which is never be used but waiting around for its child processes to die. Usually started for /etc/inittab

Also refer following blog to collect more information http://theperfectarts.com/