I STORAGE [initandlisten] exception in initAndListen: 28574 Cannot start server. Detected data files in /data/db created by storage engine 'wiredTiger'. The configured storage engine is 'mmapv1'., terminating ....
https://docs.mongodb.com/manual/tutorial/change-standalone-wiredtiger/ I found this link thinking of any help but it says that you have to start mongod first which is not starting right now.
If you have multiple nodes in a replica set, changing from MMAPv1 to WiredTiger is as simple as for each node : - stop the node - delete the database file - restart the node on WiredTiger (with --storageEngine wiredTiger if version less than 3.2)
The node will now replicate all it's database from the primary using the new format.
If you have a single node installation. You need to use mongodump/mongorestore to dump your database, stop the standalone node, remove the database directory, restart the node with WiredTiger and restore your backup.
