前言

1. Docker虚拟化技术主要是为了解决企业轻量级服务器操作系统和应用容器而诞生的，Docker虚拟化在企业中主要有两种应用方式：
   启动应用服务；
   
   启动Guest OS；
   
2. 基于Docker虚拟化平台，创建一台CentOS云主机（Guest OS），要求CentOS云主机操作系统版本：7.x（Linux内核：3.10+），同时对外启动并且监听22端口，用户通过远程工具CRT、XSHELL能够远程访问。操作的步骤和方法如下：
   #在Docker仓库中搜索CentOS镜像；
   docker search centos

[root@hecs-x-medium-2-linux-20200611091300 ~]# docker search centos
NAME                               DESCRIPTION                                     STARS               OFFICIAL            AUTOMATED
centos                             The official build of CentOS.                   6063                [OK]                
ansible/centos7-ansible            Ansible on Centos7                              130                                     [OK]
consol/centos-xfce-vnc             Centos container with "headless" VNC session…   116                                     [OK]
jdeathe/centos-ssh                 OpenSSH / Supervisor / EPEL/IUS/SCL Repos - …   114                                     [OK]
centos/systemd                     systemd enabled base container.                 84                                      [OK]
centos/mysql-57-centos7            MySQL 5.7 SQL database server                   77                                      
imagine10255/centos6-lnmp-php56    centos6-lnmp-php56                              58                                      [OK]
tutum/centos                       Simple CentOS docker image with SSH access      47                                      
centos/postgresql-96-centos7       PostgreSQL is an advanced Object-Relational …   46                                      

从Docker仓库中下载CentOS镜像；

docker pull centos
如果要安装centos7下载，这里我们下载centos最新版CentOS Linux release 8.1.1911 (Core)
docker pull ansible/centos7-ansible

查看已下载CentOS镜像文件和列表信息；

ls -l /var/lib/docker/image/overlay2/
docker images
docker images|grep -aiE centos

[root@hecs-x-medium-2-linux-20200611091300 ~]# docker images|grep -aiE centos
centos                    latest              470671670cac        5 months ago        237MB

基于CentOS镜像启动一台CentOS云主机；

docker run -itd --privileged --name=xqy_centos01 centos:latest

Run，全新创建并且启动新容器；
-i，interactive交互模式；
-t，tty打开登陆终端；
-d，detach后台运行；
-p，publish发布端口，将宿主机6022映射至容器22端口；
--name，指定或者自定义容器的名称；
--privileged，开启超级特权，支持更多的指令操作。

查看CentOS云主机运行状态和IP地址；

docker ps
docker inspect xqy_centos01|grep -ai ipaddr|tail -1

[root@hecs-x-medium-2-linux-20200611091300 ~]# docker inspect xqy_centos01|grep -ai ipaddr|tail -1
                    "IPAddress": "172.17.0.4",

进入容器

docker exec -it 0e18294d2044 /bin/bash
检查容器网络，从容器内ping外网和宿主机

[root@0e18294d2044 /]# ping  192.168.0.166
PING 192.168.0.166 (192.168.0.166) 56(84) bytes of data.
64 bytes from 192.168.0.166: icmp_seq=1 ttl=64 time=0.045 ms

[root@0e18294d2044 /]# ping www.baidu.com
PING www.a.shifen.com (182.61.200.7) 56(84) bytes of data.
64 bytes from 182.61.200.7 (182.61.200.7): icmp_seq=1 ttl=48 time=30.7 ms

从宿主机ping容器

[root@hecs-x-medium-2-linux-20200611091300 ~]# ping 172.17.0.4
PING 172.17.0.4 (172.17.0.4) 56(84) bytes of data.
64 bytes from 172.17.0.4: icmp_seq=1 ttl=64 time=0.046 ms

默认CentOS8镜像软件包不完整，需要手工添加、安装SSH服务、Net-tools工具、修改默认root密码，最后启动SSH服务方可远程。

安装Net-tools工具

[root@0e18294d2044 /]# yum -y install net-tools
Failed to set locale, defaulting to C.UTF-8
CentOS-8 - AppStream                                                                                                                                           594 kB/s | 5.8 MB     00:09    
CentOS-8 - Base                                                                                                                                                160 kB/s | 2.2 MB     00:14    
CentOS-8 - Extras                                                                                                                                              6.9 kB/s | 6.7 kB     00:00    
Dependencies resolved.
===============================================================================================================================================================================================
 Package                                    Architecture                            Version                                                      Repository                               Size
===============================================================================================================================================================================================
Installing:
 net-tools                                  x86_64                                  2.0-0.51.20160912git.el8                                     BaseOS                                  323 k

Transaction Summary

安装SSH服务

[root@0e18294d2044 /]# yum -y install openssh-server
Failed to set locale, defaulting to C.UTF-8
Last metadata expiration check: 0:07:30 ago on Sun Jun 28 02:00:13 2020.
Dependencies resolved.
===============================================================================================================================================================================================
 Package                                           Architecture                              Version                                           Repository                                 Size
===============================================================================================================================================================================================
Installing:
 openssh-server                                    x86_64                                    8.0p1-4.el8_1                                     BaseOS                                    485 k
Installing dependencies:

启动 /usr/sbin/sshd排错

报错如图

[root@0e18294d2044 /]# /usr/sbin/sshd 
Unable to load host key: /etc/ssh/ssh_host_rsa_key
Unable to load host key: /etc/ssh/ssh_host_ecdsa_key
Unable to load host key: /etc/ssh/ssh_host_ed25519_key
sshd: no hostkeys available -- exiting.
[root@0e18294d2044 /]# docker ps
bash: docker: command not found

处理办法：
1、可以从宿主机拷贝对应的文件到容器
docker cp /etc/ssh/ssh_host_rsa_key 0e18294d2044:/etc/ssh/
三个文件都要拷贝

[root@hecs-x-medium-2-linux-20200611091300 ~]# docker cp /etc/ssh/ssh_host_rsa_key 0e18294d2044:/etc/ssh/ssh_host_rsa_key
[root@hecs-x-medium-2-linux-20200611091300 ~]# docker cp /etc/ssh/ssh_host_ecdsa_key  0e18294d2044:/etc/ssh/ssh_host_ecdsa_key
[root@hecs-x-medium-2-linux-20200611091300 ~]# docker cp /etc/ssh/ssh_host_ed25519_key 0e18294d2044:/etc/ssh/ssh_host_ed25519_key

启动sshd服务

[root@0e18294d2044 /]# /usr/sbin/sshd
[root@0e18294d2044 /]# ps -ef|grep ssh
root       147     0  0 02:55 ?        00:00:00 /usr/sbin/sshd
root       154    19  0 03:01 pts/1    00:00:00 grep --color=auto ssh

基于该容器提交新的镜像

docker commit 0e18294d2044 xqy_centos8.1:ssh

[root@hecs-x-medium-2-linux-20200611091300 ~]# docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
ba06e60f6e65        xqy_centos8.1:ssh   "/bin/bash"              4 hours ago         Up 4 hours          0.0.0.0:6000->22/tcp     xqy_centos8

全新运行新镜像

 docker run -itd --privileged --name=xqy_centos8 -p 6000:22  xqy_centos8.1:ssh

进入新容器
docker exec -it ba06e60f6e65 /bin/bash
修改root密码
yum -y install passwd cracklib-dicts #安装passwd和依赖包
passwd root #密码修改为1

启动ssh 一定要去启动不然默认不会启动ssh

[root@ba06e60f6e65 /]# ps -ef|grep ssh
root        96    63  0 07:18 pts/1    00:00:00 grep --color=auto ssh
[root@ba06e60f6e65 /]# /usr/sbin/sshd 
[root@ba06e60f6e65 /]# ps -ef|grep ssh
root        98     0  0 07:18 ?        00:00:00 /usr/sbin/sshd
root       100    63  0 07:18 pts/1    00:00:00 grep --color=auto ssh

开放宿主机的访问规则

xshell工具连接成功如图

Connecting to 124.70.180.XXX:6000...
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.

WARNING! The remote SSH server rejected X11 forwarding request.
"System is booting up. Unprivileged users are not permitted to log in yet. Please come back later. For technical details, see pam_nologin(8)."
[root@ba06e60f6e65 ~]# 

快速启动多台私有云主机

for i in (seq 0 9);do docker run -itd --privileged --name=xuqy_cent0$i -p 600$i:22 xqy_centos8.1:latest ;done
#启动每一台的sshd
for i in $(docker ps -aq);do docker exec $i /usr/sbin/sshd ;done
#查看容器的IP地址
for i in $(docker ps -aq);do docker inspect $i|grep -ai ipaddr|tail -1|grep -oE "([0-9]{1,3}\.){3}[0-9]{1,3}" ;done
# 查看容器ID和容器对应的IP地址
for i in $(docker ps -aq);do echo $i; docker inspect $i|grep -ai ipaddr|tail -1|grep -oE "([0-9]{1,3}\.){3}[0-9]{1,3}" ;done

后续会增加dockerfile的制作直接将ssh服务加入到新镜像中默认启动
另外构建私有云还有很多参数可以指定比如cpu 内存 磁盘 网络等等，后续更新