A more secure alternative to NFS or SAMBA would be to use SSHFS.

Besides encrypting the data stream, it has many benefits, among which:

1. Firewall-friendly, since it uses standard SSH ports
2. Supports PKI

To mount an SSH filesystem from Ubuntu, do the following:

1. sudo apt install sshfs

2. sudo mkdir /MountPoint

3. sudo sshfs username@server:/RemoteFileSystem /MountPoint

Note: You don’t need to use sudo to mount via sshfs, just make sure you have permissions on the local mount point.

Sources:

1. https://www.digitalocean.com/community/tutorials/how-to-use-sshfs-to-mount-remote-file-systems-over-ssh