I think we have something that automatically restarts the downed service, but that's Toawa's expertise and not mine. I tend to avoid logging into the server as much as possible since I know enough to royally fuck up things, but not enough to fix it if the royal fuck up happens.
Honestly, neither Toawa nor I are willing to put in the time/effort to upgrade the existing danbooru 2 engine. If anything, since the framework is so old, you should start with a fresh copy of the latest stable build of danbooru 2 and then we can see if we can write migration scripts + offload the image assets to the new db. I'm honestly not a huge fan of DB 2, but it is what it is.
Danbooru 2 is lightweight enough that you can probably set it up on a local vm and play with it as you please, on whatever linux distro.
The problems we have are:
1) Can't turn off debug mode (wtf)
2) Our posgresql keeps losing its index / crashing / not compatible with the latest danbooru2 engine. So stuff crash and burns.
3) Not a web developer, and I have no desire to learn JS or Ruby, so no new development on our pages / bug fixes.
4) Don't have the desire/will to go through another migration. I don't touch web-server stuff on my day to day, and I have no desire to learn it.
At this point in this site's life, I'm not looking for anything ambitious. Toawa did all the hardwork last time, I just pay the bills and I think we were both surprised the migration went so smoothly.
If someone wants to take over backend server maintenance or do dev work on the frontend that's fine (since nobody's actively maintaining the site), but if something breaks and we can't bring the site back up that'll be the end of it. I don't have any desires to rollback or restart from something new and honestly, this site has been up for almost a decade and it's pretty incredible for something that started as a meme.