Network file system (nfs)
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NFS allows remote hosts to mount file systems over a network as if they were local. It uses TCP and RPC processes to facilitate sharing files between systems. Administrators can configure NFS clients and servers by editing configuration files like /etc/exports and /etc/fstab to control access and mount shared directories.
Network file system (nfs)
- 1. . NETWORK FILE SYSTEM (NFS) Linux
- 2. 1. A Network File System (NFS) allows remote hosts to mount file systems over a network and interact with those file systems as though they are mounted locally. 2. This enables system administrators to consolidate resources onto centralized servers on the network.
- 3. HOW NFS WORKS TCP is the default transport protocol for NFS version 2 and 3 under Red Hat Enterprise Linux. UDP can be used for compatibility purposes as needed, but is not recommended for wide usage. NFSv4 requires TCP. All the RPC/NFS daemons have a '-p' command line option that can set the port, making firewall configuration easier. After TCP wrappers grant access to the client, the NFS server refers to the /etc/exports configuration file to determine whether the client is allowed to access any exported file systems. Once verified, all file and directory operations are available to the user.
- 4. nfs service nfs start starts the NFS server and the appropriate RPC processes to service requests for shared NFS file systems. nfslock service nfslock start activates a mandatory service that starts the appropriate RPC processes allowing NFS clients to lock files on the server.
- 5. rpcbind rpcbind accepts port reservations from local RPC services. These ports are then made available (or advertised) so the corresponding remote RPC services can access them. rpcbind responds to requests for RPC services and sets up connections to the requested RPC service. This is not used with NFSv4.
- 6. THE FOLLOWING RPC PROCESSES FACILITATE NFS SERVICES: rpc.mountd rpc.nfsd Lockd rpc.statd rpc.rquotad rpc.idmapd
- 7. NFS CLIENT CONFIGURATION The mount command mounts NFS shares on the client side. Its format is as follows: # mount -t nfs -o options host:/remote/export /local/directory
- 8. This command uses the following variables: options A comma-delimited list of mount options; refer to Section 8.5, “Common NFS Mount Options” for details on valid NFS mount options. server The hostname, IP address, or fully qualified domain name of the server exporting the file system you wish to mount /remote/export The file system or directory being exported from the server, that is, the directory you wish to mount /local/directory The client location where /remote/export is mounted
- 9. The NFS protocol version used in Red Hat Enterprise Linux 7 is identified by the mount options nfsvers or vers. By default, mount will use NFSv4 with mount -t nfs. If the server does not support NFSv4, the client will automatically step down to a version supported by the server. If the nfsvers/vers option is used to pass a particular version not supported by the server, the mount will fail. The file system type nfs4 is also available for legacy reasons; this is equivalent to running mount -t nfs -o nfsvers=4 host:/remote/export /local/directory.
- 10. Mounting NFS File Systems using /etc/fstab An alternate way to mount an NFS share from another machine is to add a line to the /etc/fstab file. The line must state the hostname of the NFS server, the directory on the server being exported, and the directory on the local machine where the NFS share is to be mounted. You must be root to modify the /etc/fstab file.
- 11. Syntax example The general syntax for the line in /etc/fstab is as follows: server:/usr/local/pub /pub nfs defaults 0 0 The mount point /pub must exist on the client machine before this command can be executed. After adding this line to /etc/fstab on the client system, use the command mount /pub, and the mount point /pub is mounted from the server.
- 12. The /etc/fstab file is referenced by the netfs service at boot time, so lines referencing NFS shares have the same effect as manually typing the mount command during the boot process. A valid /etc/fstab entry to mount an NFS export should contain the following information: server:/remote/export /local/directory nfs options 0 0