[root tip] [How To] Share data using NFS

linux-aarhus · October 3, 2020, 4:49pm

Goal

Sharing data between 2 computer in both directions. We will apply the sharing of the ~/Music folder and we will ensure there is no duplicated data.

This guide is an application of the Arch wiki guide to NFS

Preparation

On Manjaro the package providing NFS is nfs-utils and is installed as part of the system. As the NFS service works using either IP address or hostnames it is a good idea to test if you can ping a computer using its hostname.

We will use the client/server topology so select a system with a lot of available storage as server - as it makes sense to designate the available storage to as a network share.

A server needs to be powered up and visible on the network and have a predictable address on the network.

In this guide we assume you are using Network Manager and you set a static IP for your network card. You can use WiFi but it is not as good as a wired connection.

For this guide we assume

network: 192.168.1.0
subnet: 255.255.255.0
server IP: 192.168.1.20
computername: server01

The share

As we want to avoid duplicating data we will move the relevant folder from the home folder to a designated structure and symlink the data into the home folder.

Create the data structure

On the server create the folder structure and make the share point writable by world - in this example the Music folder.

# mkdir -p /data/Music
# chmod ugo+rwx /data/Music

Move the content of the ~/Music folder to the new folder - remove the empty ~/Music folder and symlink it to the new location

$ mv ~/Music/* /data/Music/
$ rm -f ~/Music
$ ln -sf /data/Music ~/Music

Verify it is done right by listing the content of ~/Music

$ ls ~/Music

Create export folders

To share the folders using NFS we need an export point and the /srv folder is entrypoint. Create a folder to designate this is the NFS service point.

# mkdir -p /srv/nfs/Music

Server bind mount

To avoid sharing a location which could expose the system we create a bind mount in the file system table binding the data folder with the nfs export point

/etc/fstab

/data/Music /srv/nfs/Music none bind 0 0

Mount without restart

Remount the mount points using mount

# mount -a

Export the shares

Edit the file /etc/exports share the root of the NFS and the share itself and access control for the shares.

NFS works only with IP and/or hostname restrictions so it is possible to restrict further down using only IP addresses or hostnames. The example below adapted from the Arch wiki - tested and tried - it works.

Additionally you can export the same share multiple times thus limiting access to a specific share to e.g. two devices - if the device uses a dynamic IP you can specifiy hostname and get the same result as if it uses static IP. In the example below we have allowed all computers on the network to connect to the Music share

/etc/exports

/srv/nfs            192.168.1.0/24(rw,sync,crossmnt,fsid=0)
/srv/nfs/Music      192.168.1.0/24(rw,sync)

Service

Enable and start the service.

# systemctl enable --now nfs-server.service

Client

Enable and start the service

# systemctl enable --now nfs-client.target

Mounting

Manual

Using a manual or fstab mount

you would create a similar folder structure on the client

If you choose systemd units - systemd will take care of the folder creation - and all you have to do is symlink the folder when it has been mounted for the first time

fh@ts:~|⇒  tree -L 2 /data
/data
└── nfs
    └── web

Manual mount the folder from the server

$ sudo mount -t nfs server01:/Music ~/data/nfs/music

Verify the share is up by listing the content of the mount

$ ls /data/nfs/music

If you want the shared music folder to appear directly as Music on client you can symlink directly to the clients Music folder - just ensure it is empty.

ln -sf /data/nfs/music ~/Music

Mount using fstab

Using fstab requires the folder structure to present like a manual mount

The line in fstab could look like this

server01:/nfs/music   /data/nfs/music  nfs auto,x-systemd.automount,x-systemd.device-timeout=10,timeo=14,x-systemd.idle-timeout=1min 0 0

Using systemd units

The folder structure is not required as systemd will create it on first mount.
The system units are required to be named as the mount path followed by .mount

# touch /etc/systemd/system/data-nfs-music.mount

[Unit]
Description=Music
After=network.target

[Mount]
What=server01:/nfs/music
Where=/data/nfs/music
Type=nfs
Options=_netdev,auto

[Install]
WantedBy=multi-user.target

Enable the mount

# systemctl enable data-nfs-music.mount

Then the automount unit (same name rule)

# touch /etc/systemd/system/data-nfs-music.automount

[Unit]
Description=Automount music share
ConditionPathExists=/data/nfs/music

[Automount]
Where=/data/nfs/music
TimeoutIdleSec=10

[Install]
WantedBy=multi-user.target

Before you start the automount unit - ensure the share is not mounted - or the automount will fail.

Enable and start the automount

# systemctl enable --now data-nfs-music.automount

Navigate to the folder /data/nfs/music and verify the it has the content from your nfs service.

Conclusion

You have now shared your collection of music on your local network. Any change to the ~/Music folder will immediately be reflected on the network.

Background on the chosen folder tree

On the *nix filesystem we have a location named /mnt. This location is mostly used to mount filesystems to chroot into, make changes and exit. The folder is described as a place for temporary mounts Filesystem Hierachy Standard

Path Usage

/mnt Temporarily mounted filesystems.

The standard also suggests a folder for shared data

Path Usage

/srv Site-specific data served by this system, such as data and scripts for web servers, data offered by FTP servers …

The SysAdmin recommendation

What follows here is my personal experience as a sysadmin and believe me - make it simple - easily memorable - you can thank me later.

Your data

As a safeguard of your system, the actual data should be located in a separate structure. You will later be adding bind mounts for them.

The data structure can - as starting point - be anything but sticking to the recognizable - use a distinctive pattern and simple rules

Partitions mount in folders right below /data/
Shares from other systems in service/folder structure e.g. /data/nfs/data
Move local data to designated folders and use local symlinks to users home e.g. move the ~/Music to /data/local/Music and symlink the folder back ln -s /data/local/Music ~/Music

Example

Starting in /data/ your structure could look like this

/data >>> tree -L 2
.
├── build
├── nfs
│   └── data
├── smb
│   └── data
├── local
│   ├── Music
│   └── Video
├── projects
└── virtualbox

Mount your partitions using fstab

Your shares

For the data you plan to share, create a similar structure using /srv/ as base.

/srv >>> tree -L 2
.
└── nfs
     ├── Music
     └── Video

Add bind mounts to fstab - as bind mounts adds a layer of security to your shares - as you should avoid sharing anything which eventually could be used to traverse the root of your system.

/data/local/Music /srv/nfs/Music none bind 0 0    
/data/local/Video /srv/nfs/Video none bind 0 0

To avoid duplication of data you could create a symlink to your home folder - or - in case of indexing utilities like Albert which do not follow symlinks you could create an additional bind mount for the user(s) on the system.

As example - replace username with the actual username for which you would like to make the folder indexable.

/data/local/Music /home/username/Music none bind 0 0