NFS and Mounting

NFS (Network File System) allows different hosts to share directories and files over the network. It is one of the most commonly used network storage sharing protocols in Linux/Unix environments, widely used for cluster shared storage, development environment collaboration, centralized log storage, and more.

NFS Basic Architecture

NFS Server                          NFS Client
/data/shared  ----network export---->  /mnt/nfs_share (mount point)
192.168.1.10                         192.168.1.20

NFS Server Configuration

Installing the NFS Service

sudo dnf install nfs-utils -y

Starting and Enabling at Boot

sudo systemctl enable --now nfs-server

Verify the service status:

sudo systemctl status nfs-server

Creating a Shared Directory

sudo mkdir -p /data/shared
sudo chown nobody:nobody /data/shared
sudo chmod 755 /data/shared

Configuring /etc/exports

/etc/exports is the core NFS configuration file that defines which directories are shared with which clients and the associated permissions.

sudo vi /etc/exports

Add an export entry:

/data/shared    192.168.1.0/24(rw,sync,no_root_squash,no_subtree_check)

exports Configuration Details

Basic format:

shared_directory    client_address(option1,option2,...)

Client address formats:

Format	Description	Example
Single IP	Allow only one host	192.168.1.20
Subnet	Allow an entire subnet	192.168.1.0/24
Hostname	Specify a hostname	client.example.com
Wildcard	Match domain names	*.example.com
All	Allow all hosts	*

Common options:

Option	Description
rw	Read-write access
ro	Read-only access
sync	Synchronous writes; higher data safety
async	Asynchronous writes; better performance but less safe
no_root_squash	Client root has root privileges on the server
root_squash	Client root is mapped to nobody (default)
all_squash	All users are mapped to nobody
anonuid=N	Map anonymous users to the specified UID
anongid=N	Map anonymous users to the specified GID
no_subtree_check	Do not check subdirectory permissions; improves performance

Caution

no_root_squash allows clients to operate on files in the shared directory as root. Use only in fully trusted network environments. The default root_squash is recommended for production.

Multiple Directory Export Examples

# Read-write share, allow entire subnet
/data/shared      192.168.1.0/24(rw,sync,no_subtree_check)

# Read-only share, allow specific hosts
/data/public      192.168.1.0/24(ro,sync,no_subtree_check)

# Multiple clients with different permissions
/data/project     192.168.1.20(rw,sync,no_root_squash) 192.168.1.30(ro,sync)

# Map all users to a specified UID/GID
/data/upload      *(rw,sync,all_squash,anonuid=1000,anongid=1000)

Applying Export Configuration

After modifying /etc/exports, re-export the shares:

sudo exportfs -ra

View the current export list:

sudo exportfs -v

Common exportfs parameters:

Parameter	Description
-a	Export or unexport all directories
-r	Re-export all directories
-v	Verbose output
-s	Show the current export list

NFS Firewall Configuration

NFS requires multiple ports to be open in order to function properly. Using firewalld service rules is the simplest approach.

Opening NFS-Related Services

sudo firewall-cmd --permanent --add-service=nfs
sudo firewall-cmd --permanent --add-service=rpc-bind
sudo firewall-cmd --permanent --add-service=mountd
sudo firewall-cmd --reload

Verifying Firewall Rules

sudo firewall-cmd --list-all

Note

NFS v4 uses TCP port 2049 by default. If you are using NFS v4 only, opening the nfs service alone is sufficient. If you also need NFS v3 compatibility, you must additionally open rpc-bind and mountd.

NFS Client Mounting

Installing Client Tools

sudo dnf install nfs-utils -y

Viewing Directories Shared by the Server

showmount -e 192.168.1.10

Temporary Mount

sudo mkdir -p /mnt/nfs_share
sudo mount -t nfs 192.168.1.10:/data/shared /mnt/nfs_share

Verify the mount:

df -hT /mnt/nfs_share
mount | grep nfs

Mounting with a Specific NFS Version

# Use NFS v4
sudo mount -t nfs -o vers=4 192.168.1.10:/data/shared /mnt/nfs_share

# Use NFS v3
sudo mount -t nfs -o vers=3 192.168.1.10:/data/shared /mnt/nfs_share

Unmounting NFS

sudo umount /mnt/nfs_share

Persistent NFS Mounting via fstab

Basic fstab NFS Entry

Edit /etc/fstab:

sudo vi /etc/fstab

Add:

192.168.1.10:/data/shared  /mnt/nfs_share  nfs  defaults,_netdev  0  0

fstab Entry with Detailed Options

192.168.1.10:/data/shared  /mnt/nfs_share  nfs  rw,hard,timeo=600,retrans=2,_netdev  0  0

Common NFS Mount Options

Option	Description
_netdev	Marks as a network device; mount only after the network is ready
hard	Continuously retry when the server is unresponsive (default)
soft	Return an error after timeout when the server is unresponsive
timeo=N	Timeout value (in units of 0.1 seconds)
retrans=N	Number of retries
rsize=N	Read buffer size
wsize=N	Write buffer size
vers=4	Specify the NFS version
noatime	Do not update access times
nosuid	Disable SUID
noexec	Disable execution

Tip

NFS fstab entries must include the _netdev option. Otherwise, the system will attempt to mount the NFS share before the network is ready, causing boot delays or hangs.

Verifying fstab Configuration

sudo mount -a
df -hT /mnt/nfs_share

Auto-Mounting with autofs

autofs automatically mounts NFS shares when a directory is accessed and automatically unmounts them when idle, reducing resource usage.

Installing autofs

sudo dnf install autofs -y

Configuring autofs

1. Edit the master configuration file /etc/auto.master and add an auto-mount point:

   sudo vi /etc/auto.master

   Add the following line:

   /mnt/auto  /etc/auto.nfs  --timeout=300

   This means subdirectories under /mnt/auto will be automatically mounted according to the rules in /etc/auto.nfs, and automatically unmounted after 300 seconds of inactivity.

2. Create the map file /etc/auto.nfs:

   sudo vi /etc/auto.nfs

   Add mapping rules:

   shared  -rw,soft,timeo=300  192.168.1.10:/data/shared
   public  -ro,soft,timeo=300  192.168.1.10:/data/public

   This means accessing /mnt/auto/shared will automatically mount 192.168.1.10:/data/shared.

3. Start the autofs service:

   sudo systemctl enable --now autofs

4. Verify auto-mounting:

   # Access the directory to trigger auto-mount
   ls /mnt/auto/shared
   
   # Check mount status
   mount | grep auto

autofs Wildcard Mounting

If you need to automatically mount all exported directories from the server, you can use a wildcard:

/etc/auto.master

/mnt/auto  /etc/auto.nfs  --timeout=300

# /etc/auto.nfs
*  -rw,soft  192.168.1.10:/data/&

& is replaced by the subdirectory name being accessed. For example, accessing /mnt/auto/shared will automatically mount 192.168.1.10:/data/shared.

Using autofs to Mount User Home Directories

NFS + autofs is commonly used to centrally manage user home directories:

/etc/auto.master

/home  /etc/auto.home  --timeout=600

# /etc/auto.home
*  -rw,soft  nfs-server:/home/&

When a user logs in, their home directory /home/username is automatically mounted from the NFS server.

Note

When using autofs to manage home directories, make sure there are no directories under local /home that conflict with NFS exports; otherwise, mount overlay issues will occur.

NFS Troubleshooting

Client Cannot Mount

# Check network connectivity
ping 192.168.1.10

# Check if the NFS service is running
sudo systemctl status nfs-server    # Run on the server

# Check RPC services
rpcinfo -p 192.168.1.10

# Check server export list
showmount -e 192.168.1.10

# Check the firewall
sudo firewall-cmd --list-all        # Run on the server

Viewing NFS Statistics

# Server statistics
nfsstat -s

# Client statistics
nfsstat -c

# View mounted NFS information
nfsstat -m

Checking NFS Version

# View NFS versions supported by the server
cat /proc/fs/nfsd/versions

# View the version used by the client mount
nfsstat -m

Hands-On: Setting Up NFS Shared Storage

Server Configuration (192.168.1.10)

1. Install and start the NFS service:

   sudo dnf install nfs-utils -y
   sudo systemctl enable --now nfs-server

2. Create shared directories:

   sudo mkdir -p /data/shared /data/readonly
   sudo chown nobody:nobody /data/shared
   sudo chmod 755 /data/shared /data/readonly

3. Configure exports:

   cat <<EOF | sudo tee /etc/exports
   /data/shared    192.168.1.0/24(rw,sync,no_subtree_check)
   /data/readonly  192.168.1.0/24(ro,sync,no_subtree_check)
   EOF
   sudo exportfs -ra
   sudo exportfs -v

4. Configure the firewall:

   sudo firewall-cmd --permanent --add-service=nfs
   sudo firewall-cmd --permanent --add-service=rpc-bind
   sudo firewall-cmd --permanent --add-service=mountd
   sudo firewall-cmd --reload

Client Configuration (192.168.1.20)

1. Install NFS tools:

   sudo dnf install nfs-utils autofs -y

2. Verify server exports:

   showmount -e 192.168.1.10

3. Create mount points and mount via fstab:

   sudo mkdir -p /mnt/shared /mnt/readonly
   
   cat <<EOF | sudo tee -a /etc/fstab
   192.168.1.10:/data/shared    /mnt/shared    nfs  rw,_netdev,hard  0  0
   192.168.1.10:/data/readonly  /mnt/readonly  nfs  ro,_netdev,hard  0  0
   EOF
   
   sudo mount -a
   df -hT /mnt/shared /mnt/readonly

4. Test reading and writing:

   echo "NFS test" | sudo tee /mnt/shared/test.txt
   cat /mnt/shared/test.txt

NFS is a simple and efficient shared storage solution for enterprise environments. Properly configuring permissions, options, and firewall rules, combined with autofs for on-demand mounting, enables a flexible and reliable network storage infrastructure.