Ghost has recently changed fro using sqlite to MySQL as its default database. There are lots of blogs and instructions out there how to move from sqlite to MySQL, which is probably the best thing to do long term. In the short term however, simply apply the following lines of code to you docker configuration.
-e database__client=sqlite3 \ -e database__connection__filename="content/data/ghost.db" \ -e database__useNullAsDefault=true
This will specify using sqlite db rather than MySQL. Long term though it is probably best to move your deployement across incase this becomes an unsupported deployment method.
That's All Folks.