同一主机创建Mongodb4.2副本集

本文主要记录在同一台服务器上安装3个节点的过程，在同时添加三个节点（同一主机不同端口）时报如下错误：

    "errmsg" : "Found two member configurations with same _id field, members.1._id == members.2._id == MemberId(1)",

环境为CentOS8, Mongodb4.2.1

1.安装Mongodb4.2.1 参考官网

Configure the package management system (yum).
Create a /etc/yum.repos.d/mongodb-org-4.2.repo file so that you can install MongoDB directly using yum:

[mongodb-org-4.2]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.2/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.2.asc

To install the latest stable version of MongoDB, issue the following command:

sudo yum install -y mongodb-org

Alternatively, to install a specific release of MongoDB, specify each component package individually and append the version number to the package name, as in the following example:

sudo yum install -y mongodb-org-4.2.6 mongodb-org-server-4.2.6 mongodb-org-shell-4.2.6 mongodb-org-mongos-4.2.6 mongodb-org-tools-4.2.6

2. 创建不同实例的目录和文件

[root@centos8]#cd /var/lib/mongo
[root@centos8 mongo]# mkdir data1
[root@centos8 mongo]# mkdir data2
[root@centos8 mongo]# mkdir data3
[root@centos8 mongo]# vi /etc/mongod.conf

内容如下：

[root@centos8 ~]# more /etc/mongod.conf 
# mongod.conf

# for documentation of all options, see:
#   http://docs.mongodb.org/manual/reference/configuration-options/

# where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod1.log

# Where and how to store data.
storage:
  dbPath: /var/lib/mongo/data1
  journal:
    enabled: true
#  engine:
#  wiredTiger:

# how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /var/run/mongodb/mongod1.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo

# network interfaces
net:
  port: 27017
  bindIp: 0.0.0.0  # Enter 0.0.0.0,:: to bind to all IPv4 and IPv6 addresses or, alternatively, use the net.bindIpAll setting.


#security:

#operationProfiling:

replication:
  replSetName: replset
  oplogSizeMB: 10
#sharding:

## Enterprise-Only Options

#auditLog:

#snmp:

分别复制为mongdb2.conf,和mongodb3.conf
分别修改其中的内容，举例如下：

  path: /var/log/mongodb/mongod2.log
  dbPath: /var/lib/mongo/data2
  pidFilePath: /var/run/mongodb/mongod2.pid

3.启动服务

[root@centos8 mongo]# mongod -f /etc/mongod.conf
[root@centos8 mongo]# mongod -f /etc/mongod2.conf 
[root@centos8 mongo]# mongod -f /etc/mongod3.conf

4.登录一台、并配置复本集

[root@centos8 etc]# mongo
MongoDB shell version v4.2.1
rs.initiate()
replset:PRIMARY> rs.status()
replset:PRIMARY> rs.add('192.168.56.112:27018')
replset:PRIMARY> rs.add('192.168.56.112:27019')
从库执行：
命令：rs.slaveOk() ----在从节点上执行

5.验证：

主上建一个新库，并插入记录，在从库上查看

replset:PRIMARY> use test;
switched to db test
replset:PRIMARY> db.master.insert({"Ip":"192.168.0.254","node":"master"});
WriteResult({ "nInserted" : 1 })
replset:PRIMARY> show dbs;
admin   0.000GB
config  0.000GB
local   0.000GB
test    0.000GB
![image.png](https://img.haomeiwen.com/i9482651/c337062958a27aae.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

在从节点执行以下操作进行数据查询：
命令：

show dbs;
use test;
db.master.find();

image.png