A password containing special characters, especially the dollar sign, has to be put in single quotes to protect them from the command shell:

$ mongo admin -u uname -p 'password'

Each user is associated with an authentication database. So if your user is declared in admin database (and authorization activated, what MUST be done in all environment server), it's mandatory to add this param in your login command.

See authentication, and more generally security for more details and explanations.

EDIT In case of using Connection String URI Format, you can skip authentication database param, in this case 'admin' will be used by default for authentication database, and 'test' by default as target database.

Example : (your user is created in 'admin' database.)

Here's different behaviors :

authentication against 'admin', database targeted is 'test'

$ mongo --host mongodb://user:pwd@myhost:27000
$ mongo --host mongodb://user:pwd@myhost:27000/test?authSource=admin
$ mongo --host mongodb://user:pwd@myhost:27000/?authSource=admin

authentication against 'admin', database targeted is 'admin'

$ mongo --host mongodb://user:pwd@myhost:27000/admin
$ mongo --host mongodb://user:pwd@myhost:27000/admin?authSource=admin

authentication against 'test', database targeted is 'test' (will not succeed)

$ mongo --host mongodb://user:pwd@myhost:27000/test
$ mongo --host mongodb://user:pwd@myhost:27000/test?authSource=test

EDIT 2 As you really need to use mongo -h -u -p notation, create your user in your 'test' database, which will be used by default in this case :

this will authenticate against 'test' database, and target 'test' database

mongo -h 199.99.99.99:27000 -u user -p pwd

Wow so many complicated/confusing answers here.

This is as of v3.4.

Short answer.

1. Start MongoDB without access control (/data/db or where your db is).

   mongod --dbpath /data/db
   

2. Connect to the instance.

   mongo
   

3. Create the user.

   use some_db
   db.createUser(
     {
       user: "myNormalUser",
       pwd: "xyz123",
       roles: [ { role: "readWrite", db: "some_db" },
                { role: "read", db: "some_other_db" } ]
     }
   )
   

4. Stop the MongoDB instance and start it again with access control.

   mongod --auth --dbpath /data/db
   

5. Connect and authenticate as the user.

   use some_db
   db.auth("myNormalUser", "xyz123")
   db.foo.insert({x:1})
   use some_other_db
   db.foo.find({})
   

Long answer: Read this if you want to properly understand.

It's really simple. I'll dumb the following down https://docs.mongodb.com/manual/tutorial/enable-authentication/

If you want to learn more about what the roles actually do read more here: https://docs.mongodb.com/manual/reference/built-in-roles/

1. Start MongoDB without access control.

   mongod --dbpath /data/db
   

2. Connect to the instance.

   mongo
   

3. Create the user administrator. The following creates a user administrator in the admin authentication database. The user is a dbOwner over the some_db database and NOT over the admin database, this is important to remember.

   use admin
   db.createUser(
     {
       user: "myDbOwner",
       pwd: "abc123",
       roles: [ { role: "dbOwner", db: "some_db" } ]
     }
   )
   

Or if you want to create an admin which is admin over any database:

   use admin
   db.createUser(
     {
       user: "myUserAdmin",
       pwd: "abc123",
       roles: [ { role: "userAdminAnyDatabase", db: "admin" } ]
     }
   )

4. Stop the MongoDB instance and start it again with access control.

   mongod --auth --dbpath /data/db
   

5. Connect and authenticate as the user administrator towards the admin authentication database, NOT towards the some_db authentication database. The user administrator was created in the admin authentication database, the user does not exist in the some_db authentication database.

   use admin
   db.auth("myDbOwner", "abc123")
   

You are now authenticated as a dbOwner over the some_db database. So now if you wish to read/write/do stuff directly towards the some_db database you can change to it.

use some_db
//...do stuff like db.foo.insert({x:1})
// remember that the user administrator had dbOwner rights so the user may write/read, if you create a user with userAdmin they will not be able to read/write for example.

More on roles: https://docs.mongodb.com/manual/reference/built-in-roles/

If you wish to make additional users which aren't user administrators and which are just normal users continue reading below.

6. Create a normal user. This user will be created in the some_db authentication database down below.

   use some_db
   db.createUser(
     {
       user: "myNormalUser",
       pwd: "xyz123",
       roles: [ { role: "readWrite", db: "some_db" },
                { role: "read", db: "some_other_db" } ]
     }
   )
   

7. Exit the mongo shell, re-connect, authenticate as the user.

   use some_db
   db.auth("myNormalUser", "xyz123")
   db.foo.insert({x:1})
   use some_other_db
   db.foo.find({})
   

Last but not least due to users not reading the commands I posted correctly regarding the --auth flag, you can set this value in the configuration file for mongoDB if you do not wish to set it as a flag.

mongo --shell

will open the shell interface.

https://docs.mongodb.com/manual/reference/program/mongo/