1、需要啟動兩個mongodb例項，首先關閉mongodb預設開機啟動.

service mongodb stop
chkconfig mongodb off

2、複製 /etc/mongod.conf 

cp /etc/mongod.conf /etc/mongod_slave.conf

3、複製mongodb的資料庫

cp -r /data/mongodb /data/mongodb_slave
chown -R mongodb:mongodb /data/mongodb_slave

4、更改mongodb_slave.conf的配置內容

logpath=/data/log/mongod_slave.log

logappend=true

# fork and run in background
fork=true

port=27018

dbpath=/data/mongodb_slave/mongodb

# location of pidfile
pidfilepath=/var/run/mongodb/mongod_slave.pid
 

啟動主庫：

/usr/bin/numactl --interleave=all /usr/bin/mongod -f /etc/mongod.conf --master

啟動從庫：

/usr/bin/numactl --interleave=all /usr/bin/mongod -f /etc/mongod_slave.conf --slave --source 127.0.0.1:27017

7、mongo登入執行命令：

use local
db.slaves.find()
{ "_id" : ObjectId("5af2647ad59f36301ce74bbe"), "config" : { "host" : "127.0.0.1:47534", "upgradeNeeded" : true }, "ns" : "local.oplog.$main", "syncedTo" : Timestamp(1525857351, 1) }