Create a MongoDB user from commandline

The use db syntax is only supported in an interactive shell session.

If you want to change databases from an admin script, you can use db.getSiblingDB('dbname').

So your equivalent command line using --eval would be:

# MongoDB 2.6+: use createUser()
$ mongo admin -u admin -p admin --eval "db.getSiblingDB('dummydb').createUser({user: 'dummyuser', pwd: 'dummysecret', roles: ['readWrite']})"

# MongoDB 2.4: use addUser()
$ mongo admin -u admin -p admin --eval "db.getSiblingDB('dummydb').addUser('dummyuser', 'dummysecret')"

There is a section in the MongoDB manual covering Differences between interactive and scripted mongo. This includes equivalents for other interactive shell helpers such as show dbs and show collections.

Solved it by putting the commands

use dummydb
db.addUser('dummyuser', 'dummysecret')

into a .js file, and then ran MongoDB by calling:

$ mongo admin -u admin -p admin < setupMongoDB.js

That's it :-)

Above in my case didn't worked

use dummyDb

db.createUser({user: "admin",pwd: "secrectP@wd",roles: [ { role: "readWrite", db: "reporting" } ],mechanisms: [ "SCRAM-SHA-256" ]   }