通过Docker启动多个Centos以模拟分布式环境

目的

有些项目没法通过本机启动多个端口号来模拟分布式集群，需要多台机器才能模拟的时候，不想用虚拟机或者不想购买机器的时候可以通过docker启动三个Centos来模拟分布式环境。

准备环境

docker即可

开始

创建docker网络

docker network create --subnet=172.19.0.0/16 mynetwork

如果发生ip冲突，自行更换其他ip地址段，后续启动centos指定的ip需要在该地址段范围内。

启动三台centos7

docker run -itd --name centos1 --net=mynetwork --ip 172.19.0.2 -v /home/loubens/project/docker/centos1:/var centos:7 /bin/bash
docker run -itd --name centos2 --net=mynetwork --ip 172.19.0.3 -v /home/loubens/project/docker/centos2:/var centos:7 /bin/bash
docker run -itd --name centos3 --net=mynetwork --ip 172.19.0.4 -v /home/loubens/project/docker/centos3:/var centos:7 /bin/bash

其中：

• -v参数可自定义挂载需求
• -ip需要在前面指定的ip地址段内
• -itd必须带上，否则会自动退出

查看是否启动成功

docker ps

示意图：

配置centos环境

以容器centos1为例，其他容器需要执行相同的操作

• 进入centos

docker exec -it centos1 /bin/bash

• 配置yum源

# 删除之前的repo文件
rm -rf /etc/yum.repos.d/*
# 新建一个repo文件
vi /etc/yum.repos.d/Centos-Base.repo

• 将如下内容粘贴进去(源自阿里云镜像提供的repo文件)，复制后不要急着退出

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#
 
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#released updates 
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

• 由于docker创建的centos会存在着无法识别$releasever参数的情况，因此需要更换为自己的centos版本，比如我的版本是7，vi编辑的时候在普通模式下(按Esc)输入如下内容然后enter，把$releasever全部更换为7即可。

:%s/\$releasever/7/g

• 直接无脑复制如下命令，安装基本环境

yum clean all

yum makecache

yum install -y openssh-server vim lrzsz wget gcc-c++ pcre pcre-devel zlib zlib-devel ruby openssl openssl-devel patch bash-completion zlib.i686 libstdc++.i686 lsof unzip zip

yum install -y openssh*

yum install -y net-tools

yum install -y initscripts

• 修改密码

  passwd root

• 配置ssh，去掉一些必要的#号（Port、ListenAddress、PermitRootLogin前的#号)

vim /etc/ssh/sshd_config

• 无脑复制

mkdir -p /var/run/sshd

ssh-keygen -q -t rsa -b 2048 -f /etc/ssh/ssh_host_rsa_key -N '' 

ssh-keygen -q -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key -N ''

ssh-keygen -t dsa -f /etc/ssh/ssh_host_ed25519_key -N ''

/usr/sbin/sshd -D & 

• 观察ssh是否启动成功

netstat -antup | grep sshd

• 退出docker容器

exit

• 测试ssh功能，为方便展示，我新建了第四个centos容器，ip为172.19.0.5

ssh root@172.19.0.5

展示结果如下：

测试单台centos是否可用

这里编写了一个go单元测试的方法，可以查看到成功地让指定的centos容器去执行我们的命令

单机既然没有问题了，那么就可以很轻松地模拟分布式环境来进行开发测试了。