` mongod --replSet m101 --logpath "1.log" --dbpath data/rs1 --port 27017 --smallfiles --oplogSize 64 --fork`
` mongod --replSet m101 --logpath "2.log" --dbpath data/rs2 --port 27018 --smallfiles --oplogSize 64 --fork`
` mongod --replSet m101 --logpath "3.log" --dbpath data/rs3 --port 27019 --smallfiles --oplogSize 64 --fork


// create a cli connection to first instance
` mongod --port 27017`

// in the connected cli

```js


config = { _id: "m101", members:[
          { _id : 0, host : "localhost:27017"},
          { _id : 1, host : "localhost:27018"},
          { _id : 2, host : "localhost:27019"} ]
};
rs.initiate(config);


```