Forcing a slave to be primary

I was playing with MongoDB and had a replica set with two members. The servers were running as guests using VirtualBox. Because of network configuration, I cannot have a static IP. Thus, everytime I start a virtual machine, it gets a different IP address. And everytime I log into that machine, it is always secondary. So, I always force it to become primary. How did I do that? Here are the steps:

1. Log into MongoDB.

2. Use the admin database. Authenticate if needed:

> use admin

switched to db admin

> db.auth("dbadmin","dbadmin")

1

rs01:SECONDARY>

As you can see, it's a secondary machine and I want it to become the primary.

3. Get the configuration and save it to a variable:

rs01:SECONDARY> x = rs.conf()

{

        "_id" : "rs01",

        "version" : 4,

        "members" : [

                {

                        "_id" : 0,

                        "host" : "10.68.6.85:27017"

                },

                {

                        "_id" : 1,

                        "host" : "10.68.6.90:27017"

                },

                {

                        "_id" : 2,

                        "host" : "10.68.6.80:27017",

                        "arbiterOnly" : true

                }

        ]

}

4. In the above configuration, there are three (3) members of the replica set. However, only one (1) of them (_id:0) is surviving. So, remove any non-surviving machines:

rs01:SECONDARY> x.members = [x.members[0]]

[ { "_id" : 0, "host" : "10.68.6.85:27017" } ]

5. Now force reconfiguration:

rs01:SECONDARY> rs.reconfig(x,{force:"true"})

{ "ok" : 1 }

rs01:SECONDARY> rs.status()

{

        "set" : "rs01",

        "date" : ISODate("2013-06-24T20:13:57Z"),

        "myState" : 1,

        "members" : [

                {

                        "_id" : 0,

                        "name" : "10.68.6.85:27017",

                        "health" : 1,

                        "state" : 1,

                        "stateStr" : "PRIMARY",

                        "uptime" : 91,

                        "optime" : {

                                "t" : 1371582629,

                                "i" : 1

                        },

                        "optimeDate" : ISODate("2013-06-18T19:10:29Z"),

                        "self" : true

                }

        ],

        "ok" : 1

}

rs01:PRIMARY>

As you see, the machine is now the primary.