Docker --- Dockerfile创建

  在之前的部分已经介绍过Dockerfile的基础知识，下面将介绍如何使用Dockerfile来创建一个支持SSH服务的镜像。
  
  创建工作目录
    首先应先创建一个sshd_centos工作目录，在其中创建Dockerfile和sshd.sh文件:
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    [docker@localhost ~]$ mkdir sshd_centos
    [docker@localhost ~]$ cd sshd_centos/
    [docker@localhost sshd_centos]$ touch Dockerfile sshd.sh
    [docker@localhost sshd_centos]$ ls
    Dockerfile  sshd.sh
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  编写sshd.sh脚本和authorized_keys文件：
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    [docker@localhost ~]$ cat sshd_centos/sshd.sh
    #!/bin/bash
    /usr/sbin/sshd -D
    [docker@localhost ~]$ ssh-keygen -t rsa
    Generating public/private rsa key pair.
    Enter file in which to save the key (/home/docker/.ssh/id_rsa): 
    Enter passphrase (empty for no passphrase): 
    Enter same passphrase again: 
    Your identification has been saved in /opt/docker/.ssh/id_rsa.
    Your public key has been saved in /opt/docker/.ssh/id_rsa.pub.
    The key fingerprint is:
    SHA256:8HzYJxn3yPPOS3Gg1IMs+fq18DiYJezg90TUc/vTM6g docker@localhost.localdomain
    ...
    +----[SHA256]-----+
    [docker@localhost ~]$ cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
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  编写Dockerfile
    下面是Dockerfile的内容及各部分的注释，可以发现对比上一节中利用【docker commit】命令创建镜像过程，所进行的操作基本一致。
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    # 设置继承镜像
    FROM centos

    # 提供一些作者的信息
    MAINTAINER from https://extp.org by alenx(liqinghai058@live.com)

    # 下面开始执行命令
    RUN yum -y update
    RUN yum install -y openssh-server openssh-client
    RUN /usr/sbin/sshd-keygen -A
    ADD sshd.sh /sshd.sh
    RUN chmod 755 /sshd.sh
    # 开发端口
    EXPOSE 22
    # 设置自启命令
    CMD ["/sshd.sh"]
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  创建镜像
    在sshd_centos目录下，使用【docker build】命令来创建镜像。注意下，在最后还有一个'.'，表示使用当前目录中的Dockerfile。
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    [docker@localhost sshd_centos]$ sudo docker build -t ssh:dockerfile .
    Sending build context to Docker daemon 3.584 kB
    Step 1/11 : FROM centos
     ---> 49f7960eb7e4
    Step 2/11 : MAINTAINER from https://extp.org by alenx(liqinghai058@live.com)
     ---> Using cache
     ---> b47f820c5594
    Step 3/11 : RUN yum  -y update
     ---> Running in e781e5379926
     ...
     Step 11/11 : CMD /sshd.sh
     ---> Running in d14bcab5f53d
     ---> 062365674942
    Removing intermediate container d14bcab5f53d
    Successfully built 062365674942
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    命令执行完毕后，如果可见"Successfully built xxxxxxx"字样，则说明镜像创建成功。
    查看本地ssh:dockerfile镜像是否存在：
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    [docker@localhost sshd_centos]$ sudo docker images 
    REPOSITORY          TAG                 IMAGE ID            CREATED              SIZE
    ssh                 dockerfile          062365674942        About a minute ago   381 MB
    docker.io/centos    latest              49f7960eb7e4        4 weeks ago          200 MB
    docker.io/busybox   latest              8c811b4aec35        6 weeks ago          1.15 MB
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  测试镜像，运行容器
    使用刚才创建的ssh:dockerfile镜像来运行一个容器。直接启动镜像，映射容器的22端口到本地的10022端口上：
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    [docker@localhost ~]$ sudo docker run -d -p 10022:22 ssh:dockerfile
    f00c7d21c2588222dab6610ada659f769edd948fb10dce446979256ac5e6721e
    [docker@localhost ~]$ sudo docker ps
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                   NAMES
    f00c7d21c258        ssh:dockerfile      "/sshd.sh"          7 seconds ago       Up 6 seconds        0.0.0.0:10022->22/tcp   suspicious_jones
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    在宿主机上连接新建的容器：
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    [docker@localhost ~]$ ssh root@172.17.0.1 -p10022
    The authenticity of host '[172.17.0.1]:10022 ([172.17.0.1]:10022)' can't be established.
    ECDSA key fingerprint is SHA256:maneh7YayXpSZAlvZhYyR1J0y3DYfQHHB3Bi5MI5hWQ.
    ECDSA key fingerprint is MD5:13:9d:e3:9b:0e:4c:92:1a:21:ad:29:1e:18:92:7d:36.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added '[172.17.0.1]:10022' (ECDSA) to the list of known hosts.
    root@172.17.0.1's password:
    [root@f00c7d21c258 ~]#
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