db.printShardingStatus()
    --- Sharding Status ---
sharding version: {
    "_id" : 1,
    "minCompatibleVersion" : 5,
    "currentVersion" : 6,
    "clusterId" : ObjectId("55795cfdjhfjdn23f49e")
}
shards:
    {  "_id" : "shard0000",  "host" : "IP : Port" }
    {  "_id" : "shard0001",  "host" : "IP : Port" }
balancer:
    Currently enabled:  yes
    Currently running:  no
    Failed balancer rounds in last 5 attempts:  0
    Migration Results for the last 24 hours:
            No recent migrations
databases:
    {  "_id" : "admin",  "partitioned" : false,  "primary" : "config" }
    {  "_id" : "testDB",  "partitioned" : true,  "primary" : "shard0001" }

db.runCommand({ movePrimary : "testDB", to : "shard0000" })
  { "primary " : "shard0000:IP : Port", "ok" : 1 }

db.runCommand({ movePrimary : "testDB.testCollection", to : "shard0000" })
  { "ok" : 0, "errmsg" : "clone failed" }