Example on how to mount a NFS share on Ubuntu Eoan as a server and MacOS Catalina as a client.
Example assumptions (you need to adapt this):
Client PC name: Bills-MBP
(Press Cmd+Space, start 'terminal', there something like bill@Bills-MBP: is written as a prompt. Use what's written between the @ and the : as client PC name further below).
Username in Ubuntu: tux
(Press the penguin-key on your keyboard, if you have none, order a penguin keyboard sticky and place it over the ugly key with four mis-shaped squares near the space bar. Enter "terminal", start the terminal, the user name will be shown before the @ sign in the prompt. E.g. "tux@dustycray:")
PC name of Ubuntu: dustycray
(Can be found out like shown above.)
Folder on Ubuntu to be shared: /home/tux/mp3
Use whatever folder you need to share as absolute path
On the NFS-Server (Ubuntu EOAN in my case) enter in the terminal (which we opened as shown above):
id -u tux
# remember the number, use it below as anonuid (replace the 1000 there)
id -g tux
# remember the number, use it below as anongid (replace the 1001 there)
sudo nano /etc/exports
# At the end of the file add the following line, replace the path name, the Client PC Name and the two numbers with your values:
#leave with ctrl+x and confirm file saving
sudo exportfs -ra
Now on the mac, open a terminal as shown above and enter (leave /private/nfs as it is):
sudo make /private/nfs
#Replace the ubuntu pc name (dustycray) and the path (home ...) by your's now:
sudo mount -t nfs -o resvport,rw dustycray:/home/tux/mp3 /private/nfs
Then the NFS can be accessed in the path /private/nfs. In finder you will see a new entry called (e.g.) "dustycray" on the left in the section "locations", also in file-open dialogs.
Above's mount procedure is not permanent, I use a script to mount it whenever I need it. However, you can also make the mount permanent if you like (e.g. System preferences / Users&Groups / Login Items / + / Select any root folder within (!) the NFS share / Add).