Problem

The following describes the process of configuring NFS using an installation of RHEL/CentOS.

Notable

On RHEL 7, NFSv4 is the default version used and maintains backwards compatibility with earlier protocols.
The meaning of the export table options (rw, all_squash, etc.) can be found using the command man exports.
Check out the man pages for fstab format and options for the nfs file systems using the command man 5 nfs.

Solution

Setup NFS Server

Install required utilities for NFS

 yum -y install rpcbind nfs-utils policycoreutils-python

Create NFS server share directory
```
 mkdir -p /srv/nfsexport
```
Set ownership of the directory
```
 chown -R nfsnobody:nfsnobody /srv
```
Set permissions of the directory
```
 chmod -R 755 /srv/*
```
Change the label of /srv/nfsexport, recursively, to the nfs_t type in order to allow the NFS server to access share.
```
 semanage fcontext --add --type nfs_t "/srv/nfsexport(/.*)?"
```
Apply the SELinux policy setting to the file system
```
 restorecon -R -v /srv/nfsexport
```
Start the NFS server
```
 systemctl start nfs-server
```
Enable the service to start at boot
```
 systemctl enable nfs-server
```
Update NFS server export table to share the newly created directory
```
 echo "/srv/nfsexport *(rw,all_squash)" >> /etc/exports
```
Notice This allows both read and write requests on this NFS volume and maps all UID/GID to the anonymous user.
Make all changes effective by reloading the configuration file.
```
exportfs -r
```

Open firewall for NFS server

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

Verify the NFS share has been mounted
```
showmount -e localhost
```

Setup NFS Client

Attempt to access the NFS server

 NFS_SERVER="" \
 && showmount -e $NFS_SERVER

Create the mount point
```
 mkdir -p /mnt/nfsshare
```

Create an /etc/fstab entry for the NFS server

 NFS_SERVER="" \
 && echo "$NFS_SERVER:/srv/nfsexport /mnt/nfsshare nfs defaults 0 0" >> /etc/exports

Mount the exported NFS share directory
```
 mount -a
```

Verify the NFS share is mounted and writable

 touch /mnt/nfsshare/test.txt
 ls -l /mnt/nfsshare

Summary

NFS is an Internet Standard protocol created by Sun Microsystems in 1984. NFS was developed to allow file sharing between systems residing on a local area network.

In NFS, an NFS server is offering shares, which are also referred to as exports, and the NFS client mounts the share to it’s local file system and supports three versions of the NFS protocol: NFS version 2 RFC1094, NFS version 3 RFC1813, and NFS version 4 RFC3530.

To use an NFS, you should follow these two steps:

Mount it - attach the local file system found on some device to the big tree file tree, the file hierarchy, rooted at / of the server.
Access it - mount the NFS share into the local file system of the NFS client computer.

Troubleshooting

If you’re using iptables for configuring security instead of firewalld, use the following commands to open the firewall for the NFS server:

    # Set the firewall rules to allow access to the NFS service
    iptables -I INPUT 1 -p tcp --dport 2049 -j ACCEPT
    iptables -I INPUT 1 -p tcp --dport 20049 -j ACCEPT
    iptables -I INPUT 1 -p tcp --dport 111 -j ACCEPT

    # Save the firewall rules
    service iptables save