MongoDB - admin user not authorized

Question

I am trying to add authorization to my MongoDB.
I am doing all this on Linux with MongoDB 2.6.1.
My mongod.conf file is in the old compatibility format
(this is how it came with the installation).

1) I created admin user as described here in (3)

http://docs.mongodb.org/manual/tutorial/add-user-administrator/

2) I then edited mongod.conf by uncommenting this line

auth = true

3) Finally I rebooted the mongod service and I tried to login with:

/usr/bin/mongo localhost:27017/admin -u sa -p pwd

4) I can connect but it says this upon connect.

MongoDB shell version: 2.6.1
connecting to: localhost:27017/admin
Welcome to the MongoDB shell!
The current date/time is: Thu May 29 2014 17:47:16 GMT-0400 (EDT)
Error while trying to show server startup warnings: not authorized on admin to execute command { getLog: "startupWarnings" }

5) Now it seems this sa user I created has no permissions at all.

root@test02:~# mc
MongoDB shell version: 2.6.1
connecting to: localhost:27017/admin
Welcome to the MongoDB shell!
The current date/time is: Thu May 29 2014 17:57:03 GMT-0400 (EDT)
Error while trying to show server startup warnings: not authorized on admin to execute command { getLog: "startupWarnings" }
[admin] 2014-05-29 17:57:03.011 >>> use admin
switched to db admin
[admin] 2014-05-29 17:57:07.889 >>> show collections
2014-05-29T17:57:10.377-0400 error: {
        "$err" : "not authorized for query on admin.system.namespaces",
        "code" : 13
} at src/mongo/shell/query.js:131
[admin] 2014-05-29 17:57:10.378 >>> use test
switched to db test
[test] 2014-05-29 17:57:13.466 >>> show collections
2014-05-29T17:57:15.930-0400 error: {
        "$err" : "not authorized for query on test.system.namespaces",
        "code" : 13
} at src/mongo/shell/query.js:131
[test] 2014-05-29 17:57:15.931 >>>

What is the problem? I repeated this whole procedure 3 times and
I think I did it all as specified in the MongoDB docs. But it doesn't work.
I was expecting this sa user to be authorized to do anything so that
he can then create other users and give them more specific permissions.

Answer 1

I was also scratching my head around the same issue, and everything worked after I set the role to be root when adding the first admin user.

use admin
db.createUser(
  {
    user: 'admin',
    pwd: 'password',
    roles: [ { role: 'root', db: 'admin' } ]
  }
);
exit;

If you have already created the admin user, you can change the role like this:

use admin;
db.grantRolesToUser('admin', [{ role: 'root', db: 'admin' }])

For a complete authentication setting reference, see the steps I've compiled after hours of research over the internet.