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NFSv4, network file system version 4, is the new version of NFS (for setting up the older NFSv3, see Nfs) with new features like strong authentication and integrity via Kerberos and SPKM-3, improved performance, safe file caching, lock migration, UTF-8, ACLs and better support for Windows file sharing semantics.

This article covers installing and configuring NFSv4.

Installing

Both client and servers require the nfs-utils package. Install with pacman:

# pacman -S nfs-utils

Configuring

Server

The server configuration is very thorough.

Exports

First we'll need to edit our exports in /etc/exports. A typical NFSv4 export would look like this:

/export    192.168.0.12(rw,fsid=0,no_subtree_check,async,no_root_squash)
/export/music 192.168.0.12(rw,no_subtree_check,async,no_root_squash)

/export is the NFS root here (due to the fsid=0 entry). Everything else that you want to be shared over NFS must be accessible under /export.

For exporting directories outside the NFS root, see below.

Exporting directories outside your NFS root

To do this, you'll need to use bind mounts. For example, to bind /home/john to /export/john:

# mount --bind /home/john /export/john

Then, /export/john needs to be added to /etc/exports:

/export    192.168.0.12(rw,fsid=0,no_subtree_check,async,no_root_squash)
/export/music 192.168.0.12(rw,no_subtree_check,async,no_root_squash)
/export/john 192.168.0.12(rw,no_subtree_check,async,no_root_squash,nohide)

The nohide option is required, because the kernel NFS server automatically hides mounted directories. To add the bind mount to /etc/fstab:

/home/john    /export/john    none    bind  0 0

ID mapping

Then, /etc/idmapd.conf needs to be edited. You'll need to at the very least specify your Domain there. Example:

[General]
Verbosity = 1
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
Domain = archlinux.org
[Mapping]
Nobody-User = nobody
Nobody-Group = nobody

/etc/hosts.allow

To allow network access to the nfs server you should edit /etc/hosts.allow. The following example opens these services to anyone:

nfsd: ALL
rpcbind: ALL
mountd:ALL

This is a very insecure way of allowing host access. To get better control over who is allowed to access the daemons, hosts.deny should be everyone, and hosts.allow should specifically allow certain people. In this example, 192.168.0.101 should be the IP address of the person(s) allowed to access it. The numbers after the '/' is the netmask:

nfsd: 192.168.0.101/255.255.255.255
rpcbind: 192.168.0.101/255.255.255.255
mountd: 192.168.0.101/255.255.255.255

This examples enables access for anyone on that network:

nfsd: 192.168.0.0/255.255.255.0
rpcbind: 192.168.0.0/255.255.255.0
mountd: 192.168.0.0/255.255.255.0

For finer control, read the hosts_access(5) man page.

Starting the server

To start the NFS server, just do:

# /etc/rc.d/rpcbind start
# /etc/rc.d/nfs-common start
# /etc/rc.d/nfs-server start

If you want to tweak the configuration, feel free to edit /etc/conf.d/nfs-server.conf to fit your needs.

Client

The client configuration is more simple.

Client ID mapping

/etc/idmapd.conf needs to be edited on all clients and the Domain entry should be identical to the one on the server. Example:

[General]
Verbosity = 1
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
Domain = archlinux.org
[Mapping]
Nobody-User = nobody
Nobody-Group = nobody
[Translation]
Method = nsswitch

/etc/hosts.allow

You will need to allow rpcbind for the server's ip:

 rpcbind: 192.168.0.100/255.255.255.255

Mounting the partitions on the client

On the client, to mount the NFSv4 partition: Make sure that nfs module is loaded. (lsmod | grep nfs). If not execute the next command "modprobe nfs"

# /etc/rc.d/rpcbind start
# /etc/rc.d/nfs-common start
# mount -t nfs4 server:/ /mnt/server/
# mount -t nfs4 server:/music /mnt/music/
# mount -t nfs4 server:/john /mnt/john

Replacing 'server' with the hostname or IP address of your NFS server and of course 'server', 'music' and 'john' with the names of whatever directories you exported on the server.

If you want the NFS volumes to mount automatically on bootup, add them to fstab. For example:

server:/ /mnt/server nfs4 async,user 0 0

Remember to add netfs in the daemons array at /etc/rc.conf in order to mount nfs volumes at boot.

Client & Server: Time Synchronization

In order for NFS to function properly, both server and client must have closely matching time values. If the clocks on the clients differ from the server too much, then basic functions like file copy operations may hang for a very long time leaving the system unusable until they resume. The clocks do not have to match to micro/nano second accuracies, but ideally they should be within 1 second of each other.

The NTP system is recommended to sync both the server and the clients to the highly accurate NTP servers available on the Internet. For a small system like a home network, the ntpdate utility may be used to sync both servers and clients to the same time. For a larger installation, it may be desirable to install an OpenNTP server (see NTP) onto the same machine acting as the NFS server, and then all clients on the network would sync time values from the server. This has the advantage of lowering the stress on the external NTP servers, and in assuring that the NFS clients will use the exact time that the NFS server has, even if the NFS server experiences some drift.

Troubleshooting

Common problems and how to overcome them

messages.log contains "nfsdopenone: Opening /proc/net/rpc/nfs4.nametoid/channel failed: errno 2 (No such file or directory)"

Add 'nfsd' to /etc/rc.conf modules array (NOTE: you may need to add "Verbosity = 3" to /etc/idmapd.conf and restart the services above to receive the error)

exportfs: /etc/exports:2: syntax error: bad option list

Delete all space from the option list in /etc/exports

mount.nfs4: No such device

Check that you have loaded nfs module

lsmod | grep nfs

and if previous returns empty or only nfsd-stuff, do

modprobe nfs

mount.nfs4: access denied by server while mounting

Check that the permissions on your client's folder are correct ('755' worked for me --Zenlord 12:01, 7 May 2010 (EDT))