If rpc.lockd is not started, file locking will fail. Rpc.lockd - allows NFS clients to lock files on the server. It works with the Linux kernel to meet the dynamic demands of NFS clients, such as providing server threads each time an NFS client connects. Rpc.nfsd - Allows explicit NFS versions and protocols the server advertises to be defined. Nfs service and does not require user configuration. This process is started automatically by the Rpc.mountd - This process receives mount requests from NFS clients and verifies the requested file system is currently exported. The mounting and locking protocols have been incorpated into the V4 protocol which eliminates the need for interaction with rpc.mountd and rpc.lockd. NFSv4 listens on the well known TCP port (2049) which eliminates the need for the portmapper interaction. NFSv4 has no interaction with portmapper, rpc.mountd, rpc.lockd, and rpc.statd, since protocol support has been incorporated into the v4 protocol. For this reason, TCP is the preferred protocol when connecting to an NFS server. However, because UDP is stateless, if the server goes down unexpectedly, UDPР”В¬lients continue to saturate the network with requests for the server. The NFS server can be restarted without affecting the clients and the cookie remains intact. This file handle is an opaque object stored on the server's side and is passed along with RPC requests from the client. The NFS server sends the client a file handle after the client is authorized to access the shared volume. When using NFSv2 or NFSv3 with UDP, the stateless UDP connection under normal conditions has less Protocol overhead than TCP which can translate into better performance on very clean, non-congested networks. ( UDP) running over an IP network to provide a stateless network connection between the client and server. NFSv2 and NFSv3 can use the User Datagram Protocol System via NFS, Red Hat Enterprise Linux uses NFSv3 by default, if the server supports it.Р”Р„ll versions of NFS can use Transmission Control Protocol ( TCP) running over an IP network, with NFSv4 requiring it. Red Hat Enterprise Linux supports NFSv2, NFSv3, and NFSv4 clients, and when mounting a file NFS version 4 (NFSv4) works through firewalls and on the Internet, no longer requires portmapper, supports ACLs, and utilizes stateful operations. NFS version 3 (NFSv3) has more features, including 64bit file handles, Safe Async writes and more robust error handling. NFS version 2 (NFSv2) is older and is widely supported. Currently, there are three versions of NFS.

What is nfs protocol