MongoDB shell version: 2.2.3
connecting to: /tmp/mongodb-27017.sock:27017/test
repl0:PRIMARY> use admin
switched to db admin
repl0:PRIMARY> db.runCommand('getCmdLineOpts')
{
	"argv" : [
		"./mongod",
		"--dbpath",
		"/storage/data/rs0",
		"--port",
		"27017",
		"--replSet",
		"repl0",
		"--keyFile",
		"/home/behackett/work/key"
	],
	"parsed" : {
		"dbpath" : "/storage/data/rs0",
		"keyFile" : "/home/behackett/work/key",
		"port" : 27017,
		"replSet" : "repl0"
	},
	"ok" : 1
}
repl0:PRIMARY> db.sytem.users.find()
repl0:PRIMARY> db.addUser('admin', 'pass')
{
	"user" : "admin",
	"readOnly" : false,
	"pwd" : "e4e538f5dcb52537cad02bbf8491693c",
	"_id" : ObjectId("511583981babfde6e653926b")
}
addUser succeeded, but cannot wait for replication since we no longer have auth

> db.auth('admin', 'pass')
1
repl0:PRIMARY> 

./mongo --host /tmp/mongodb-27017.sock
MongoDB shell version: 2.2.3
connecting to: /tmp/mongodb-27017.sock:27017/test
> use admin
switched to db admin
> db.runCommand('getCmdLineOpts')
{ "errmsg" : "need to login", "ok" : 0 }
> db.system.users.find()
error: {
	"$err" : "unauthorized db:admin ns:admin.system.users lock type:1 client:",
	"code" : 10057
}
> 

./mongo
MongoDB shell version: 2.2.3
connecting to: test
> use admin
switched to db admin
> db.runCommand('getCmdLineOpts')
{
	"argv" : [
		"./mongod",
		"--dbpath",
		"/Users/behackett/data/db",
		"--auth"
	],
	"parsed" : {
		"auth" : true,
		"dbpath" : "/Users/behackett/data/db"
	},
	"ok" : 1
}