so how long did you have Pi-hole running successfully on that device?
Around a month i think.
and I assume that you recently ran pihole -up and that's when things went wrong?
yes when the release came up on the admin console
Thats what backups are for.
Or filesystem snaps like with ZFS.
You cant expect to be able to fix every problem so need provision fallback.
and you were on the main release. I just want to make sure you didn't pihole checkout dev
yes the main release, i had upgraded a couple of times before without an issue, first i knew of a problem was last night when i got a you don't have permission in the web interface and then it wouldn't let me ssh in. so i've been trying to figure out what has gone wrong and it seems it is letting it reconfigure the firewall that breaks things.
does anything else on the device have a webui?
Yes I used to do some web development stuff on it at one time but I havent used it much for that for a long time pi-holes about the only new thing in about a year.
I think i'll probably compress the broken image put the base install on resize that and then i can pick up the config files from the broke system.
pretty sure just port 80 , i did have a couple of media servers , plex and twonky but they used to fall over a lot so i decided to make it a itunes share instead.
any of that running on a port that isn't 80?
so its going to have to be rebuilt again? unless any of you fellas can figure out a fix.
Rebuilding would be the quickest resolution to the problem,
I was just trying to troubleshoot what was still working, and see if it was salvageable.
if I could get ssh working... i think i'd lose it if i tried a chroot ..
Some more things you can check on the SSD:
- Disk full;
- Filesystem errors (run "fsck" on the unmounted partitions);
- Whats in the log files.
And when you get everything working again, try setup console via serial port (USB) for next time when you lose network.
1 and 2 fine 3- systemd 
will need another serial port from somewhere 
I dont understand what you mean with "3- systemd" ?
Did you or did you not check the logs residing in the /var/log folder ?
It seems the board already got a serial port:
Just need to put console redirect on kernel line with right parameters and connect cable.
systemd doesn't log to text files, which makes it hard to see whats going on with the log files. Pi-hole logging to a text file is quite handy as I could see that it was up and running so that at least meant that the box was up and running. I had a little mount problem a while ago. I had a data drive with a mount point defined in the fstab. Without that drive connected systemd was halting the boot process and going into an emergency shell, with no way of communicating with it it was hard to identify the problem.
The flash has a small mod that directs it to look outside the box first. Without the ssd the box boots up as a standard iconnect. I've had it a good few years now, cost €50 new.
I do have a prolific usb serial cable, but just 1 it would be handy but 99% of the time this box just works, the last rebuild was because the 4GB flash drive i was booting from failed after several years of 24/7 use. There are a few of these on ebay (still around €50). I've even run gimp on this box and firefox You can get a usb sound card running on them as well.
The base system is available here congenio GmbH - Debian auf der Iomega iConnect