用Dockerfile创建一个具有ssh服务的基础Ubuntu镜像

1.创建文件目录与文件

创建所需的目录sshd_ubuntu用于存放Dockerfile和相关文件。

$    mkdir sshd_ubuntu/
$   cd sshd_ubuntu/
$   touch Dockerfile sources.list

2.修改sources.list文件

修改sources.list文件以更换docker的镜像源。此处用户请自行修改对应源，作者基础镜像为ubuntu14.04。

deb http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty main restricted universe multiverse
#deb-src http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty main restricted universe multiversedeb http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-security main restricted universe multiverse
#deb-src http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-security main restricted universe multiversedeb http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-updates main restricted universe multiverse
#deb-src http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-updates main restricted universe multiverse#deb http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-backports main restricted universe multiverse
#deb-src http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-backports main restricted universe multiverse#deb http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-proposed main restricted universe multiverse
#deb-src http://linux.xidian.edu.cn/mirrors/ubuntu/ trusty-proposed main restricted universe multiverse

3.Dockerfile内容

#build ssh images
#
#VERSION        1.0FROM ubuntu:14.04
MAINTAINER NSS/Czh#更换国内源文件
COPY    ./sources.list /etc/apt/sources.list
RUN     apt-get update \&& echo "#!/bin/sh\nexit 0" > /usr/sbin/policy-rc.d \&& DEBIAN_FRONTEND="noninteractive" apt-get install -y openssh-server \&& rm -rf /var/lib/apt/lists/*
#设置用于ssh连接的root密码
RUN     echo 'root:xidian'|chpasswd
RUN     mkdir -p /var/run/sshd
#允许root连接
RUN     sed -i 's/PermitRootLogin without-password/PermitRootLogin yes/g' /etc/ssh/sshd_configEXPOSE  22
CMD     ["/usr/sbin/sshd", "-D"]

启动/停止ssh服务，可以将 /usr/sbin/policy-rc.d 文件中的返回值改为0。echo “#!/bin/sh\nexit 0” > /usr/sbin/policy-rc.d。参考文章docker报错：invoke-rc.d: policy-rc.d denied execution of start.

设置DEBIAN_FRONTEND环境变量为noninteractive后，会进行静默安装（非交互模式），非交互模式会选择默认的选项并以最快的速度完成构建。请确保只在Dockerfile中调用的RUN命令中设置了该选项，而不是使用ENV命令进行全局的设置。因为ENV命令在整个容器运行过程中都会生效，所以当你通过BASH和容器进行交互时，如果进行了全局设置那就会出问题。（此处不加DEBIAN_FRONTEND="noninteractive"也可正常运行，暂时不清楚原因），参考文章ubuntu DEBIAN_FRONTEND环境变量用法

4.创建镜像

$ docker build -t ubuntu/sshd:1.0 .
Step 1/9 : FROM ubuntu:14.04---> 2c5e00d77a67
Step 2/9 : MAINTAINER NSS/Czh---> Using cache---> 5097a7552add
Step 3/9 : COPY ./sources.list /etc/apt/sources.list---> Using cache---> 8312d88d1cd1
Step 4/9 : RUN  apt-get update  && echo "#!/bin/sh\nexit 0" > /usr/sbin/policy-rc.d    && DEBIAN_FRONTEND="noninteractive" apt-get install -y openssh-server    && rm -rf /var/lib/apt/lists/*---> Running in 6b7d56b01900
...篇幅问题过程略...
Creating SSH2 RSA key; this may take some time ...
Creating SSH2 DSA key; this may take some time ...
Creating SSH2 ECDSA key; this may take some time ...
Creating SSH2 ED25519 key; this may take some time ...* Starting OpenBSD Secure Shell server sshd...done.
Setting up python2.7 (2.7.6-8ubuntu0.5) ...
Setting up python-minimal (2.7.5-5ubuntu3) ...
Setting up python (2.7.5-5ubuntu3) ...
Setting up python-chardet (2.0.1-2build2) ...
Setting up python-six (1.5.2-1ubuntu1.1) ...
Setting up python-urllib3 (1.7.1-1ubuntu4.1) ...
Setting up python-requests (2.2.1-1ubuntu0.4) ...
Setting up tcpd (7.6.q-25) ...
Setting up ssh-import-id (3.21-0ubuntu1) ...
Processing triggers for libc-bin (2.19-0ubuntu6.15) ...
Processing triggers for ca-certificates (20170717~14.04.2) ...
Updating certificates in /etc/ssl/certs... 148 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d....done.
Processing triggers for ureadahead (0.100.0-16) ...
Removing intermediate container 6b7d56b01900---> 4aa044c39969
Step 5/9 : RUN  echo 'root:xidian'|chpasswd---> Running in 87f783382399
Removing intermediate container 87f783382399---> 4480a39550f4
Step 6/9 : RUN  mkdir -p /var/run/sshd---> Running in 48aad77ee015
Removing intermediate container 48aad77ee015---> cef0534f0337
Step 7/9 : RUN  sed -i 's/PermitRootLogin without-password/PermitRootLogin yes/g' /etc/ssh/sshd_config---> Running in de50ae4a8fad
Removing intermediate container de50ae4a8fad---> bca8c53762a1
Step 8/9 : EXPOSE   22---> Running in 5c6de8f317ad
Removing intermediate container 5c6de8f317ad---> 2ed7a44408af
Step 9/9 : CMD  ["/usr/sbin/sshd", "-D"]---> Running in 66b881fc6b1b
Removing intermediate container 66b881fc6b1b---> 365c22c94b4f
Successfully built 365c22c94b4f
Successfully tagged ubuntu/sshd:4.0

可以使用docker images命令看到当前创建

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
ubuntu/sshd         1.0                 365c22c94b4f        16 hours ago        230MB

5. 测试镜像，运行容器

我们运行一个镜像，启动一个命令，用docker ps -a查看所有容器

$ docker run -d -p 101:22 ubuntu/sshd:1.0
84bf42e0da86989ed9ccf857f1778d375f2216d337064aa3a8eed6048012cc4d
$ docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                      PORTS                 NAMES
84bf42e0da86        ubuntu/sshd:1.0     "/usr/sbin/sshd -D"      8 seconds ago       Up 6 seconds                0.0.0.0:101->22/tcp   competent_babbage

此时容器已正常运行。
测试：
在另一台主机用ssh连接容器宿主机ip和端口号ssh root@ip -p port

ubuntu@ubuntu:~/.ssh$ ssh root@192.168.8.95 -p 101
The authenticity of host '[192.168.8.95]:101 ([192.168.8.95]:101)' can't be established.
ECDSA key fingerprint is SHA256:0wD3wI2oB4/20Qe3daLklQ1z+0UslHlV2t/ZDQNV/yw.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[192.168.8.95]:101' (ECDSA) to the list of known hosts.
root@192.168.8.95's password:
Welcome to Ubuntu 14.04 LTS (GNU/Linux 4.4.0-146-generic x86_64)* Documentation:  https://help.ubuntu.com/The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.root@84bf42e0da86:~#

测试成功，创建的ssh镜像可以正常使用。