MongoDB UserNotFound when starting mongod I have a MongoDB version 2.4 that i wish to upgrade to 4.0. The official solution is to upgrade from 2.4 to 2.6, then to 3.0, and so on.
I am attempting to upgrade from 2.6 to 3.0, and also to change the storage engine to WiredTiger .
To upgrade from 2.6 to 3.0 i changed the bin folder's name of the 2.6executables and then changed the 3.0 bin folder's name to bin (so i will have a seamless transition to 3.0). Then as This official MongoDB upgrade manual says, i am trying to change the storage engine to WiredTiger by using This manual.
However, when i run this command:
mongod --storageEngine wiredTiger --dbpath ../dataDb_WiredTiger

as suggested by the manual, i get an error:

SCRAM-SHA-1 authentication failed for MyAdminUser on admin ;
UserNotFound Could not find user MyAdminUser@admin
Failed to authenticate MyAdminUser@admin with mechanism MONGODB-CR: AuthenticationFailed UserNotFound Could not find user MyAdminUser@admin

But using MongoVUE or shell, i am able to authenticate using the same user.
What am i missing here?
Thank you.
Ended up working by using a configuration file when running mongod. Don't know why.