My Mastodon instance crashed this morning due to a combination of the usual running out of space issue and me being too lazy to remember to remove federated media regularly from my instance BEFORE it crashes. Now I know you can schedule this with CRON jobs but for some reason I've never been able to configure that correctly nor have I been motivated to get to the bottom of it.
Anyway, I went through the usual dance of starting up my services and using the CLI to clean up my instance.
However, none of my commands worked because it couldn't connect to the database. A quick look at the status showed the database and all my services were running which led me to go down a troubleshooting rabbit hole with no end in sight and little guidance as to what might be the problem.
Eventually, before gave up I thought, "my instance is down anyway, couldn't I just turn it off and on again?" I did exactly that and when it restarted I was able to continue with my cleanup tasks as normal.
So as a reminder, if all else fails, try turning it off and on again.