Last part of the puzzle was that the php-fpm service wasn’t running.
Started it with:

sudo systemctl start php-fpm.service sudo systemctl enable php-fpm.service systemctl status php-fpm.service

And now the FOG Web UI is working for me again.

@tadziuuu Just to be clear on a few points.

The .iso / memdisk route only works for bios based computers. This will not work for uefi based computers.

With the .iso image files and the parameter block I previously provided, you get the error message about initramfs? If yes, then I suspect the fetch command is not downloading the squashfs filesystem. I copied that command over from your initial parameter block. It looks like we need to focus on that bit then.

@sebastian-roth I would be happy to give you a feedback if I have the opportunity to test your new init (I am an intern so opportunities do not arise all the time :))

@wmw509 Disabling CSM makes sense. I’ve seen a lot of bioses that if CSM is enabled it only lets you use the legacy/bios pxe boot. I’ve had that disabled on all my hardware for so long I forgot it was a thing.

@Eazis Sounds good, thanks for the feedback!

yes, /etc/hosts as told in my post indeed, and /etc/resolv.conf as well. All information required to be fetched a way or another. Be it by a custom client or something else.

@Wayne-Workman I do not know. Pinging directly may be a better option, but I would not recommend it. ICMP is not really a good mechanism to test up/down state. This is because ICMP knows nothing about the host, nor does it really care. Remember, we aren’t directly tracking the IP of a host any more, and this is for good reason in my eyes. Basically, the current mechanism knows what host is what because it translates the Hostname to its corresponding IP address. If you want to just know if a host is “pingable” then you should probably add the Host IP field back and enter the corresponding host’s IP address. This way, even if the host is currently rebooting, it will respond if the network is up and running.

For future readers, this is most commonly an FTP credentials problem, and the answer is located here: https://wiki.fogproject.org/wiki/index.php/Troubleshoot_FTP#Credentials_.2F_Passwords

There have been major improvements made in the area of your problem on FOG Trunk. Also, 1.2.0 has known instabilities on Ubuntu 14.04 and newer. These instabilities are also fixed in FOG Trunk.

Here is how you would upgrade to trunk: https://wiki.fogproject.org/wiki/index.php/Upgrade_to_trunk

If you don’t wish to use FOG Trunk, you’ll have to wait for help from someone more experienced than myself.