If you would read the post and he did not edited the post after your questions you could read: “After some searches, i could resolve the issue by restarting the nfs service… The portmapper caused troubles for me as well, so i include it here :”

Depending on the type or problems you are having will probably determine what you want to backup and what you want to discard.

You can export most of the host, images defs, group, and other information from the database. You can backup your /images directory to another location, and you can copy your .fogsettings file so you know what you chose during the install.

SOLVED !
Indeed, to reply to your message, I stayed connected to internet during the installation of Fog, and disconnected as soon as possible. I ran the installation twice in fact (once while connected, the other time disconnected).

Anyway, here’s the cause of the problem -which makes me feel dumb…
The person who worked before I came configured a 066 option in the extended field.
I didn’t knew anything about that ; I did my configuration in the main DHCP field.
His PXE came first and the PXE was done on a server (still in use) that no longer hosts a up to date PXE.
…
Thank you for your support. Now It’s (at least) time for fun !! 🙂