Sooo…
I was going to write the following text, which I will now leave in, in case anybody ever stumbles upon the same issue. I had a faulty Symlink to my Backup Drive, which appearently died…
This couldn’t be resolved by the WebUI. Caught it in the last second before sending the reply 
Thank you very much @hexparrot
Ah, thank you! I only looked in the wiki.
So, however I didn’t get it to run. Here are the command line things I tried:
root@Greger …/games/minecraft# netstat -tnl | grep 8443
root@Greger …/games/minecraft# ps -aux | grep node
root 6717 0.0 0.0 11108 1004 pts/0 S+ 21:38 0:00 grep --color=auto node
root@Greger …/games/minecraft# supervisorctl status mineos
mineos FATAL Exited too quickly (process log may have details)
root@Greger …/games/minecraft# supervisorctl restart mineos
mineos: ERROR (not running)
mineos: ERROR (spawn error)
root@Greger …/games/minecraft# git log -n 1 | grep commit
commit 5670b46c4f22e806ce5819a7f86042df4b4ecc23
I guess you need to see only one line in the log, as they seem to repeat with only new timestamps (and the latest run of the update script):
Script execution started on: Tue Sep 15 18:50:19 CEST 2020
Updating mineos-node repository…OK
Pulling master branch…Already up-to-date.
OK
Updating npm dependencies…audited 575 packages in 4.983s
found 2 vulnerabilities (1 moderate, 1 high)
- run
npm audit fix
to fix them, or npm audit
for details*
OK
Setting node javascript files to executable…OK
Script execution ended on: Tue Sep 15 18:50:28 CEST 2020
{“date”:“Wed Sep 16 2020 21:33:10 GMT+0200 (CEST)”,“process”:{“pid”:6499,“uid”:0,“gid”:0,“cwd”:"/usr/games/minecraft",“execPath”:"/usr/bin/node",“version”:“v8.17.0”,“argv”:["/usr/bin/node","/usr/games/minecraft/webui.js"],“memoryUsage”:{“rss”:47329280,“heapTotal”:22888448,“heapUsed”:15910056,“external”:422733}},“os”:{“loadavg”:[0.0791015625,0.0244140625,0.02783203125],“uptime”:95914},“trace”:[{“column”:18,“file”:“fs.js”,“function”:“Object.fs.mkdirSync”,“line”:885,“method”:“mkdirSync”,“native”:false},{“column”:9,“file”:"/usr/games/minecraft/node_modules/fs-extra/lib/mkdirs/mkdirs-sync.js",“function”:“Object.mkdirsSync”,“line”:31,“method”:“mkdirsSync”,“native”:false},{“column”:6,“file”:"/usr/games/minecraft/server.js",“function”:“new server.backend”,“line”:27,“method”:“backend”,“native”:false},{“column”:12,“file”:"/usr/games/minecraft/webui.js",“function”:null,“line”:173,“method”:null,“native”:false},{“column”:30,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:null,“line”:1108,“method”:null,“native”:false},{“column”:37,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:null,“line”:166,“method”:null,“native”:false},{“column”:13,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:null,“line”:726,“method”:null,“native”:false},{“column”:16,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:null,“line”:52,“method”:null,“native”:false},{“column”:17,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:“done”,“line”:246,“method”:null,“native”:false},{“column”:16,“file”:"/usr/games/minecraft/node_modules/async/lib/async.js",“function”:null,“line”:44,“method”:null,“native”:false}],“stack”:[“Error: EEXIST: file already exists, mkdir ‘/var/games/minecraft/backup’”," at Object.fs.mkdirSync (fs.js:885:18)"," at Object.mkdirsSync (/usr/games/minecraft/node_modules/fs-extra/lib/mkdirs/mkdirs-sync.js:31:9)"," at new server.backend (/usr/games/minecraft/server.js:27:6)"," at /usr/games/minecraft/webui.js:173:12"," at /usr/games/minecraft/node_modules/async/lib/async.js:1108:30"," at /usr/games/minecraft/node_modules/async/lib/async.js:166:37"," at /usr/games/minecraft/node_modules/async/lib/async.js:726:13"," at /usr/games/minecraft/node_modules/async/lib/async.js:52:16"," at done (/usr/games/minecraft/node_modules/async/lib/async.js:246:17)"," at /usr/games/minecraft/node_modules/async/lib/async.js:44:16"],“level”:“error”,“message”:“uncaughtException: EEXIST: file already exists, mkdir ‘/var/games/minecraft/backup’”,“timestamp”:“2020-09-16T19:33:10.508Z”}
Hope somebody can give me a hint, or is it easier to just reinstall MineOS?