What is NFS ?#

NFS, Network File System, is a distributed file system protocol used for sharing files and directories over a network. The files and directories can be accessed as if they were located on the remote computer.

Installing NFS server#

The following core packages need to be installed:

sudo apt-get update
sudo apt-get install nfs-kernel-server rpcbind -y

sudo yum update
sudo yum install nfs-utils rpcbind -y

Once the packages are installed, you can start the NFS server service.

sudo systemctl start nfs-server
sudo systemctl start rpcbind

Optionally, you may want to configure the service to auto-start on boot.

sudo systemctl enable nfs-server
sudo systemctl enable rpcbind

Sharing Directories with NFS#

Files or folders to be accessed by NFS clients are configured in the file /etc/exports.
This file is maintained by the system administrator.

Lines beginning with a # are treated as comments while empty lines are ignored.
A basic directory entry is in the following format:

[folder_path] [network_address](export_options)

NOTE

There is no space between network_address and export_options

Multiple allowed network addresses can also be specified for a single directory entry as follows:

[folder_path] [network_address_1](export_options) [network_address_2](export_options)

# allow clients by ip
/folders/myfolder1  192.168.22.10(rw,anoguid=34,anouid=34)
/folders/myfolder1  192.168.22.11(rw,anoguid=34,anouid=34)

# allow all ips in a network
/folders/myfolder2  192.168.22.0/24(rw,anoguid=12,anouid=12)

# allow multiple networks
/folders/myfolder3  192.168.22.0/24(rw) 192.168.23.0/24(rw,anoguid=12,anouid=12)

# using patterns to specify network address
/folders/myfolder4  192.168.*.0/24(rw) 192.168.23.0/24(rw)

# reload exports file
sudo exportfs -r

# view exported directory and file entries
sudo exportfs -v

Mounting NFS Shares in Linux#

Only clients specified, or match the rules specified, in /etc/exports can mount shared NFS directories. NFS client package must be installed to mount NFS directories: nfs-utils in Red Hat based distros and nfs-common in Debian based distros.

sudo apt-get update
sudo apt-get install nfs-common -y

sudo yum update
sudo yum install nfs-utils -y

Once the packages are installed, the NFS share can be mounted using mount command.

mount -t nfs nfs_server:folder_path mount_point -o mount_options

NOTE

The mount_point must be a valid path in the client.

# mount /folders/myfolder1 shared by 168.10.100 at /mount_point
mount -t nfs 192.168.10.100:/folders/myfolder1 /mount_point

192.168.10.100:/folders/myfolder1  /mount_point    nfs  defaults                     0 0
192.168.10.100:/folders_00         /mount_point_2  nfs  defaults,nfsvers=4,tcp,bg    0 0

# unmount by nfs_server:folder_path
umount 192.168.10.100:/folders/myfolder1

# unmount by mount_point
umount /mount_point

NFSv4 Only Server#

NFSv2 and NFSv3 rely on three core services: nfsd, mountd, and lockd. These services do not have fixed ports. When they start, they bind to dynamic ports. They then register the chosen ports with the rpcbind service. NFS clients have to query the rpcbind service on the server to discover the specific port numbers for each necessary NFS function.

NFSv4 integrates these functions into the main NFSv4 protocol itself. The protocol also uses a fixed well-known port, 2049/tcp, for communication. This eliminates the need for these decoupled services and hence the need for rpcbind service.

To run NFSv4 only server, all legacy NFS versions need to be disabled. In this case rpcbind is not needed and can be disable or masked. This is the recommended approach for a secure NFS server deployment.

[nfsd]
vers2=n
vers3=n

sudo systemctl restart nfs-server

cat /proc/fs/nfsd/versions

# disable rpcbind
sudo systemctl disable --now rpcbind

# stop and mask rpcbind service
sudo systemctl stop rpcbind
sudo systemctl mask rpcbind

Summary#

• nfs-kernel-server, nfs-utils, rpcbind packages are needed to run an NFS server depending on the desired NFS version and the server Linux distro.
• NFS shares are configured in ‘/etc/exports’
• NFS shares can be mounted on the client’s file system just like client local drives.
• NFS shares can be added to /etc/fstab, hence being mounted on system startup.
• For secure NFS deployments, prefer NFSv4 as it has evolved to a more secure protocol than v2 and v3.

Conclusion#

You should now be able to:

• Deploy a secure NFS server.
• Mount and unmount NFS shares on local file system.
• Troubleshoot NFS server related problems.
• Troubleshoot permission issues when dealing with mounted NFS shares.

NOTE

Happy File Sharing !!!