# 使用Docker快速部署不同版本CentOS容器
> 本文是快速部署CentOS系列Docker容器的快速指南
## 下载各个系列CentOS docker基础镜像
* 下载CentOS 5/6/7 版本基础镜像
```
sudo docker pull centos:5
sudo docker pull centos:6
sudo docker pull centos:7
```
* 检查下载的镜像：
```
sudo docker images
```
可以看到如下输出
```
REPOSITORY TAG IMAGE ID CREATED SIZE
docker.io/centos 7 196e0ce0c9fb 5 weeks ago 197 MB
docker.io/centos 6 5dedbd63518e 6 weeks ago 194 MB
docker.io/centos 5 1ae98b2c895d 14 months ago 285 MB
```
## 启动各版本创建一个基础容器
### CentOS5容器
```
sudo docker run -it --hostname centos5 --name centos5 docker.io/centos:5 /bin/bash
```
注意：CentOS 5已经停止镜像，但是可以通过 下载更新，所以编辑 `/etc/yum.repos.d/CentOS-Vault.repo`（只需要这个配置文件就可以）
```
[C5.11-base]
name=CentOS-5.11 - Base
baseurl=http://vault.centos.org/5.11/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
enabled=1
[C5.11-updates]
name=CentOS-5.11 - Updates
baseurl=http://vault.centos.org/5.11/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
enabled=1
[C5.11-extras]
name=CentOS-5.11 - Extras
baseurl=http://vault.centos.org/5.11/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
enabled=1
[C5.11-centosplus]
name=CentOS-5.11 - Plus
baseurl=http://vault.centos.org/5.11/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
enabled=1
[base-source]
name=CentOS-$full_releasever - Base source
baseurl=http://vault.centos.org/5.11/os/Source/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
priority=1
enabled=1
[updates-source]
name=CentOS-$full_releasever - Updates Source
baseurl=http://vault.centos.org/5.11/updates/Source/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
priority=1
enabled=1
```
> 这里同时激活了`base-source`和`updates-source`源，可以方便下载SRPM进行自己的编译安装。
>
> 补充：
>
> 但是CentOS 5系列依然缺少一些基础软件（例如`git`），可参考[CentOS 5平台通过yum安装git](https://github.com/huataihuang/cloud-atlas-draft/tree/6f3204fffc11cf006abd394631e2598d98b415c3/os/linux/redhat/package/install_git_on_centos5_using_yum/README.md)方法，添加EPEL的软件仓库作为补充：
```
sudo rpm -Uvh http://dl.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
```
### CentOS6容器
```
sudo docker run -it --hostname centos6 --name centos6 docker.io/centos:6 /bin/bash
```
### CentOS7容器
```
sudo docker run -it --hostname centos7 --name centos7 docker.io/centos:7 /bin/bash
```
## 升级和安装
* 进入容器安装必要的软件包
```
yum clean all
yum update
yum -y install sudo which mlocate net-tools rsyslog file ntp ntpdate \
wget tar bzip2 screen sysstat unzip nfs-utils parted lsof man bind-utils \
gcc gcc-c++ make telnet flex autoconf automake ncurses-devel crontabs \
zlib-devel git openssh-clients openssh-server initscripts
```
> 默认的docker镜像中不安装ssh客户端（5）或ssh服务器（7），并且CentOS 7不安装 `initscripts` 软件包，则会缺乏`/etc/rc.d/init.d/functions`这样的`/etc/init.d`目录下`sysv`基础脚本，会导致一些传统脚本失效或报错（例如，无法执行`sshd-keygen`）。
* CentOS 5/6激活sshd
```
/etc/init.d/sshd start
chkconfig sshd on
```
* CentOS 7激活sshd
```
ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa
/usr/sbin/sshd
```
> CentOS 7上也可以使用`sshd-keygen`来生成服务器的key，然后就可以启动`/usr/sbin/sshd`
>
> 实际轻量级微服务部署的docker，不需要安装如此多的软件，应该部署一个精简容器，只启动必要的服务 - 下次实践一个Django容器
## 制作镜像
```
sudo docker commit centos5 local:centos5
sudo docker commit centos6 local:centos6
sudo docker commit centos7 local:centos7
```
此后检查镜像
```
[huatai@devstack ~]$ sudo docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
local centos7 89d417f57e5e 12 seconds ago 459 MB
local centos6 6d071df1d7cb 48 seconds ago 428 MB
local centos5 d0fcf242634d 2 minutes ago 546 MB
docker.io/centos 7 196e0ce0c9fb 5 weeks ago 197 MB
docker.io/centos 6 5dedbd63518e 6 weeks ago 194 MB
docker.io/centos 5 1ae98b2c895d 14 months ago 285 MB
```
## 使用镜像创建容器
* centos 5
```
sudo docker run -it --hostname dev5 --name dev5 local:centos5 /bin/bash
```
* centos 6
```
sudo docker run -it --hostname dev6 --name dev6 local:centos6 /bin/bash
```
* centos 7
```
sudo docker run -it --hostname dev7 --name dev7 local:centos7 /bin/bash
```
## 添加ssh密钥
* 通过Dockerfilei添加ssh密钥
为了实现ssh登陆到docker容器中，建议使用的是密钥登陆方式。docker支持将host主机中的文件添加到容器中，可以在`Dockerfile`使用的指令是`ADD`。此外，在`docker build`指令时候，也可以通过`--build-arg`将host主机上的密钥内容转换成变量传递给docker，以便在Dockerfile中引用。
> 参考 [Using SSH keys inside docker container](https://stackoverflow.com/questions/18136389/using-ssh-keys-inside-docker-container)
举例，以下添加一个github账号的私钥到容器中，以便能够方便开发
```
# Setup for ssh onto github
RUN mkdir -p /root/.ssh
ADD id_rsa /root/.ssh/id_rsa
RUN chmod 700 /root/.ssh/id_rsa
RUN echo "Host github.com\n\tStrictHostKeyChecking no\n" >> /root/.ssh/config
```
以下Dockerfile中将源代码目录复制到docker容器中，并且将私钥复制到容器中，安装nodejs模块，映射端口，最后启动服务，是一个比较完整的案例，值得参考
```
#DOCKER-VERSION 0.3.4
from ubuntu:12.04
RUN apt-get update
RUN apt-get install python-software-properties python g++ make git-core openssh-server -y
RUN add-apt-repository ppa:chris-lea/node.js
RUN echo "deb http://archive.ubuntu.com/ubuntu precise universe" >> /etc/apt/sources.list
RUN apt-get update
RUN apt-get install nodejs -y
ADD . /src
ADD ../../home/ubuntu/.ssh/id_rsa /root/.ssh/id_rsa
RUN cd /src; npm install
EXPOSE 808:808
CMD [ "node", "/src/app.js"]
```
> 在[Using SSH Private keys securely in Docker build](http://blog.cloud66.com/using-ssh-private-keys-securely-in-docker-build/)也有一个比较有意思的解决方法，是通过在docker容器中运行wget，从host主机的一个本地运行的web服务器上下载密钥，也算一种解决方法：
```
FROM ubuntu
... usual apt-get steps + adding github to known_hosts
RUN wget -O ~/.ssh/id_rsa http://192.168.99.1:8080/secrets/file/id_rsa && ssh -T git@github.com && rm ~/.ssh/id_rsa
```
## 通过Dockerfile创建镜像
上述手工完成的工作，可以改写成Dockerfile如下
* Dockerfile
```
FROM docker.io/centos:5
MAINTAINER vincent huatai
RUN yum clean all
RUN yum -y update
RUN yum -y install which mlocate net-tools rsyslog file ntp ntpdate \
wget tar bzip2 screen sysstat unzip nfs-utils parted lsof man bind-utils \
gcc gcc-c++ make telnet flex autoconf automake ncurses-devel crontabs \
zlib-devel git openssh-clients openssh-server initscripts
# Add ssh public key for login
RUN mkdir -p /root/.ssh
ADD authorzied_keys /root/.ssh/authorzied_keys
RUN chmod 600 /root/.ssh/authorzied_keys
RUN chmod 700 /root/.ssh
```
* 执行命令
```
docker build -t local:centos5 .
```
* 从构建的镜像启动容器
```
docker run -itd --hostname dev5 --name dev5 local:centos5 /bin/bash
```
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