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# NFS

From ArchWiki

Summary
Article covers configuration of NFSv4 which is an open standard network file sharing protocol.
Related
NFS Troubleshooting - Dedicated article for common problems and solutions.

From Wikipedia:

  Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed.

## Installation

Both client and server only require the installation of the nfs-utils package.

Note: It is HIGHLY recommended to use a time sync daemon on ALL nodes of your network to keep client/server clocks in sync. Without accurate clocks on all nodes, NFS can introduce unwanted delays! The NTP system is recommended to sync both the server and the clients to the highly accurate NTP servers available on the Internet.

## Configuration

### Server

#### ID mapping

Edit `/etc/idmapd.conf` and set the `Domain` field to your domain name.

    /etc/idmapd.conf

    [General]

    Verbosity = 1
    Pipefs-Directory = /var/lib/nfs/rpc_pipefs
    Domain = atomic

    [Mapping]

    Nobody-User = nobody
    Nobody-Group = nobody

#### File system

Note: For security reasons, it is recommended to use an NFS export root which will keep users limited to that mount point only. The following example illustrates this concept.

Define any NFS shares in `/etc/exports` which are relative to the NFS root. In this example, the NFS root will be `/srv/nfs4` and we will be sharing `/mnt/music`.

    # mkdir -p /srv/nfs4/music

Read/Write permissions must be set on the music directory so clients may write to it.

Now mount the actual target share, `/mnt/music` to the NFS share via the mount command:

    # mount --bind /mnt/music /srv/nfs4/music

To make it stick across server reboots, add the bind mount to `fstab`:

    /etc/fstab

    /mnt/music /srv/nfs4/music  none   bind   0   0

#### Exports

Add directories to be shared and an ip address or hostname(s) of client machines that will be allowed to mount them in `exports`:

    /etc/exports

    /srv/nfs4/ 192.168.0.1/24(rw,fsid=root,no_subtree_check)
    /srv/nfs4/music 192.168.0.1/24(rw,no_subtree_check,nohide) # note the nohide option which is applied to mounted directories on the file system.

Users need-not open the share to the entire subnet; one can specify a single IP address or hostname as well.

For more information about all available options see `man 5 exports`.

If you modify `/etc/exports` while the server is running, you must re-export them for changes to take effect:

    # exportfs -rav

#### Starting the server

Start `rpc-idmapd` and `rpc-mountd` services. If you want it running at boot time, enable it. Note that these units require other services, which are launched automatically by systemd.

#### Firewall configuration

To enable access through a firewall, tcp and udp ports 111, 2049, and 20048 need to be opened. To configure this for iptables, edit `/etc/iptables/iptables.rules` to include the following lines:

    /etc/iptables/iptables.rules

    -A INPUT -p tcp -m tcp --dport 111 -j ACCEPT
    -A INPUT -p tcp -m tcp --dport 2049 -j ACCEPT
    -A INPUT -p tcp -m tcp --dport 20048 -j ACCEPT
    -A INPUT -p udp -m udp --dport 111 -j ACCEPT
    -A INPUT -p udp -m udp --dport 2049 -j ACCEPT
    -A INPUT -p udp -m udp --dport 20048 -j ACCEPT

To apply changes, restart `iptables` service.

### Client

Clients need nfs-utils to connect, and to avoid an approx 15 seconds delay with an accompanying error in dmsg that reads, "RPC: AUTH_GSS upcall timed out," users will need to start `rpc-gssd` service on any client.

Note: NFS4 servers do not need to run this service.

#### Mounting from Linux

Show the server's exported filesystems:

    $ showmount -e servername

Then mount omitting the server's NFS export root:

    # mount -t nfs4 servername:/music /mountpoint/on/client

##### /etc/fstab settings

Using fstab is useful for a server which is always on, and the NFS shares are available whenever the client boots up. Edit `/etc/fstab` file, and add an appropriate line reflecting the setup. Again, the server's NFS export root is omitted.

    /etc/fstab

    servername:/music   /mountpoint/on/client   nfs4   rsize=8192,wsize=8192,timeo=14,intr,_netdev	0 0

Note: Consult the NFS and mount man pages for more mount options.

Some additional mount options to consider are include:

rsize and wsize
  The `rsize` value is the number of bytes used when reading from the server. The `wsize` value is the number of bytes used when writing to the server. The default for both is 1024, but using higher values such as 8192 can improve throughput. This is not universal. It is recommended to test after making this change, see #Performance tuning.

timeo
  The `timeo` value is the amount of time, in tenths of a second, to wait before resending a transmission after an RPC timeout. After the first timeout, the timeout value is doubled for each retry for a maximum of 60 seconds or until a major timeout occurs. If connecting to a slow server or over a busy network, better performance can be achieved by increasing this timeout value.

intr
  The `intr` option allows signals to interrupt the file operation if a major timeout occurs for a hard-mounted share.

_netdev
  The `_netdev` option tells the system to wait until the network is up before trying to mount the share. systemd assumes this for NFS, but anyway it is good practice to use it for all types of networked filesystems

##### Using autofs

Using autofs is useful when multiple machines want to connect via NFS; they could both be clients as well as servers. The reason this method is preferable over the earlier one is that if the server is switched off, the client will not throw errors about being unable to find NFS shares. See autofs#NFS network mounts for details.

#### Mounting from Windows

Note: Only the Ultimate and Enterprise editions of Windows 7 and the Enterprise edition of Windows 8 include "Client for NFS".

NFS shares can be mounted from Windows if the "Client for NFS" service is activated (which it is not by default). To install the service go to "Programs and features" in the Control Panel and click on "Turn Windows features on or off". Locate "Services for NFS" and activate it as well as both subservices ("Administrative tools" and "Client for NFS").

Some global options can be set by opening the "Services for Network File System" (locate it with the search box) and right click on client > properties.

Warning: Serious performance issues may occur (it randomly takes 30-60 seconds to display a folder, 2 MB/s file copy speed on gigabit LAN, ...) to which Microsoft does not have a solution yet.[1]

To mount a share using Explorer:

`Computer` > `Map network drive` > `servername:/srv/nfs4/music`

#### Mounting from OS X

Note: OS X by default uses an insecure (>1024) port to mount a share.

Either export the share with the `insecure` flag, and mount using Finder:

`Go` > `Connect to Server` > `nfs://servername/`

Or, mount the share using a secure port using the terminal:

    # mount -t nfs -o resvport servername:/srv/nfs4 /Volumes/servername

## Tips and tricks

### Performance tuning

In order to get the most out of NFS, it is necessary to tune the `rsize` and `wsize` mount options to meet the requirements of the network configuration.

### Automatic mount handling

This trick is useful for laptops that require nfs shares from a local wireless network. If the nfs host becomes unreachable, the nfs share will be unmounted to hopefully prevent system hangs when using the hard mount option. See https://bbs.archlinux.org/viewtopic.php?pid=1260240#p1260240

Make sure that the NFS mount points are correctly indicated in `/etc/fstab`:

    $ cat /etc/fstab

    lithium:/mnt/data           /mnt/data	        nfs noauto,noatime,rsize=32768,wsize=32768,intr,hard 0 0
    lithium:/var/cache/pacman   /var/cache/pacman	nfs noauto,noatime,rsize=32768,wsize=32768,intr,hard 0 0

The `noauto` mount option tells systemd not to automatically mount the shares at boot. systemd would otherwise attempt to mount the nfs shares that may or may not exist on the network causing the boot process to appear to stall on a blank screen.

In order to mount NFS share by non-root user `user` may be required to be added to fstab entry. Also enable rpc-statd.service.

Create the `auto_share` script that will be used by cron to check if the NFS host is reachable,

    /root/bin/auto_share

    #!/bin/bash

    SERVER="YOUR_NFS_HOST"

    MOUNT_POINTS=$(sed -e '/^.*#/d' -e '/^.*:/!d' -e 's/\t/ /g' /etc/fstab | tr -s " " | cut -f2 -d" ")

    ping -c 1 "${SERVER}" &>/dev/null

    if [ $? -ne 0 ]; then
        # The server could not be reached, unmount the shares
        for umntpnt in ${MOUNT_POINTS}; do
            umount -l -f $umntpnt &>/dev/null
        done
    else
        # The server is up, make sure the shares are mounted
        for mntpnt in ${MOUNT_POINTS}; do
            mountpoint -q $mntpnt || mount $mntpnt
        done
    fi

    # chmod +x /root/bin/auto_share

Create the root cron entry to run `auto_share` every minute:

    # crontab -e

    * * * * * /root/bin/auto_share

A systemd unit file can also be used to mount the NFS shares at startup. The unit file is not necessary if NetworkManager is installed and configured on the client system. See #NetworkManger dispatch.

    /etc/systemd/system/auto_share.service

    [Unit]
    Description=NFS automount

    [Service]
    Type=oneshot
    RemainAfterExit=yes
    ExecStart=/root/bin/auto_share

    [Install]
    WantedBy=multi-user.target

Now enable `auto_share`.

#### NetworkManger dispatcher

In addition to the method described previously, NetworkManager can also be configured to run a script on network status change.

Enable and start the `NetworkManager-dispatcher` service.

The easiest method for mount shares on network status change is to just symlink to the `auto_share` script:

    # ln -s /root/bin/auto_share /etc/NetworkManager/dispatcher.d/30_nfs.sh

Or use the following mounting script that checks for network availability:

    /etc/NetworkManager/dispatcher.d/30_nfs.sh

    #!/bin/bash

    SSID="CHANGE_ME"

    MOUNT_POINTS=$(sed -e '/^.*#/d' -e '/^.*:/!d' -e 's/\t/ /g' /etc/fstab | tr -s " " | cut -f2 -d" ")

    ISNETUP=$(nmcli dev wifi | \grep $SSID | tr -s ' ' | cut -f 10 -d ' ') 2>/dev/null

    # echo "$ISNETUP" >> /tmp/nm_dispatch_log

    if [[ "$ISNETUP" == "yes" ]]; then
        for mntpnt in ${MOUNT_POINTS}; do
            mountpoint -q $mntpnt || mount $mntpnt
        done
    else
        for srvexp in ${MOUNT_POINTS}; do
            umount -l -f $srvexp &>/dev/null
        done
    fi

Now when the wireless SSID "CHANGE_ME" goes up or down, the `nfs.sh` script will be called to mount or unmount the shares as soon as possible.

### Configure NFS fixed ports

If you have a port-based firewall, you might want to set up a fixed ports. For rpc.statd and rpc.mountd you should set following settings in `/etc/conf.d/nfs-common` and `/etc/conf.d/nfs-server` (ports can be different):

    /etc/conf.d/nfs-common

    STATD_OPTS="-p 4000 -o 4003"

    /etc/conf.d/nfs-server

    MOUNTD_OPTS="--no-nfs-version 2 -p 4002"

    /etc/modprobe.d/lockd.conf

    # Static ports for NFS lockd
    options lockd nlm_udpport=4001 nlm_tcpport=4001

After restart `nfs-common` `nfs-server` daemons and reload `lockd` modules you can check used ports with following command:

    $ rpcinfo -p

       program vers proto   port  service
        100000    4   tcp    111  portmapper
        100000    3   tcp    111  portmapper
        100000    2   tcp    111  portmapper
        100000    4   udp    111  portmapper
        100000    3   udp    111  portmapper
        100000    2   udp    111  portmapper
        100024    1   udp   4000  status
        100024    1   tcp   4000  status
        100021    1   udp   4001  nlockmgr
        100021    3   udp   4001  nlockmgr
        100021    4   udp   4001  nlockmgr
        100021    1   tcp   4001  nlockmgr
        100021    3   tcp   4001  nlockmgr
        100021    4   tcp   4001  nlockmgr
        100003    2   tcp   2049  nfs
        100003    3   tcp   2049  nfs
        100003    4   tcp   2049  nfs
        100003    2   udp   2049  nfs
        100003    3   udp   2049  nfs
        100003    4   udp   2049  nfs
        100005    3   udp   4002  mountd
        100005    3   tcp   4002  mountd

Then, you need to open the ports 111-2049-4000-4001-4002-4003 TCP and UDP.

## Troubleshooting

There is a dedicated article NFS Troubleshooting.

## See also

- See also Avahi, a Zeroconf implementation which allows automatic discovery of NFS shares.
- HOWTO: Diskless network boot NFS root
- Very helpful
- If you are setting up the Arch Linux NFS server for use by Windows clients through Microsoft's SFU, you will save a lot of time and hair-scratching by looking at this forum post first !
- Microsoft Services for Unix NFS Client info
- Unix interoperability and Windows Vista Prerequisites to connect to NFS with Vista

Retrieved from "https://wiki.archlinux.org/index.php?title=NFS&oldid=276947"
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- File systems
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