创建ssh 服务的镜像

$ sudo docker run -ti ubuntu:14.04  /bin/bash
#首先，使用我们最熟悉的 「-ti」参数来创建一个容器。
root@fc1936ea8ceb:/# sshd
bash: sshd: command not found
#使用 sshd 开启 ssh server 服务,发现没有安装这个服务,注意，我们在使用 「-ti /bin/bash」 进入容器后，获得的是 root 用户的bash
root@fc1936ea8ceb:/# apt-get install openssh-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package openssh-server
#现有缓存里面也找不到该软件，看来官方精简的够彻底啊
root@fc1936ea8ceb:/# apt-get update
#使用「apt-get update」来更新 apt 软件源信息，如果觉得默认的国外源速度慢的话，也可以替换为国内 163souhu 等镜像的源。
Ign http://archive.ubuntu.com trusty InRelease
Ign http://archive.ubuntu.com trusty-updates InRelease
Ign http://archive.ubuntu.com trusty-security InRelease
Ign http://archive.ubuntu.com trusty-proposed InRelease
...
Fetched 20.4 MB in 2min 55s (116 kB/s)
Reading package lists... Done
root@fc1936ea8ceb:/# apt-get install openssh-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  ca-certificates krb5-locales libck-connector0 libedit2 libgssapi-krb5-2
  libidn11 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib libwrap0 libx11-6
  libx11-data libxau6 libxcb1 libxdmcp6 libxext6 libxmuu1 ncurses-term
  openssh-client openssh-sftp-server openssl python python-chardet
  python-minimal python-requests python-six python-urllib3 python2.7
  python2.7-minimal ssh-import-id tcpd wget xauth
Suggested packages:
  krb5-doc krb5-user ssh-askpass libpam-ssh keychain monkeysphere rssh
  molly-guard ufw python-doc python-tk python2.7-doc binutils binfmt-support
The following NEW packages will be installed:
  ca-certificates krb5-locales libck-connector0 libedit2 libgssapi-krb5-2
  libidn11 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib libwrap0 libx11-6
  libx11-data libxau6 libxcb1 libxdmcp6 libxext6 libxmuu1 ncurses-term
  openssh-client openssh-server openssh-sftp-server openssl python
  python-chardet python-minimal python-requests python-six python-urllib3
  python2.7 python2.7-minimal ssh-import-id tcpd wget xauth
0 upgraded, 38 newly installed, 0 to remove and 29 not upgraded.
Need to get 7599 kB of archives.
After this operation, 35.3 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
#安装一个 ssh 服务，都需要下载安装这么多的依赖
Get:1 http://archive.ubuntu.com/ubuntu/ trusty/main libedit2 amd64 3.1-20130712-2 [86.7 kB]
Get:2 http://archive.ubuntu.com/ubuntu/ trusty-proposed/main libkrb5support0 amd64 1.12+dfsg-2ubuntu5 [30.0 kB]
Get:3 http://archive.ubuntu.com/ubuntu/ trusty-proposed/main libk5crypto3 amd64 1.12+dfsg-2ubuntu5 [79.9 kB]
Get:4 http://archive.ubuntu.com/ubuntu/ trusty/main libkeyutils1 amd64 1.5.6-1 [7318 B]
Get:5 http://archive.ubuntu.com/ubu
...
Updating certificates in /etc/ssl/certs... 164 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d....done.
Processing triggers for ureadahead (0.100.0-16) ...
root@fc1936ea8ceb:/# mkdir -p /var/run/sshd
#创建 ssh 服务运行需要的目录
root@fc1936ea8ceb:/# /usr/sbin/sshd -D &
#在后台运行 ssh 服务
[1] 3254
root@fc1936ea8ceb:/# netstat -tunlp
#查看服务端口是否正常
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      -
tcp6       0      0 :::22                   :::*                    LISTEN      -
root@fc1936ea8ceb:/# mkdir root/.ssh
root@fc1936ea8ceb:/# vi /root/.ssh/authorized_keys
#复制需要登陆到这个台机器的公钥到 authorized_keys 文件中
root@fc1936ea8ceb:/# sed -ri 's/session    required     pam_loginuid.so/#session    required     pam_loginuid.so/g' /etc/pam.d/sshd
#修改 ssh 服务的安全登陆配置
root@fc1936ea8ceb:/# vi /run.sh
#创建可执行文件run.sh，详细内容见后文
root@fc1936ea8ceb:/# chmod +x run.sh
#添加可执行权限
root@fc1936ea8ceb:/# exit
exit
$ sudo docker commit  fc1 sshd:ubuntu
#使用 「docker commit」 将现在这个容器保存为 sshd:ubuntu 镜像
7aef2cd95fd0c712f022bcff6a4ddefccf20fd693da2b24b04ee1cd3ed3eb6fc
$ sudo docker  images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
sshd                ubuntu              7aef2cd95fd0        10 seconds ago      255.2 MB
busybox             latest              e72ac664f4f0        3 weeks ago         2.433 MB
ubuntu              latest              ba5877dc9bec        3 months ago        192.7 MB
#验证一下，我们目前拥有的镜像
$ sudo docker  run -p 100:22  -d sshd:ubuntu /run.sh
#启动容器，并映射端口 100 -->22，100 是宿主主机的端口，22 是容器的 ssh 端口
3ad7182aa47f9ce670d933f943fdec946ab69742393ab2116bace72db82b4895
$ sudo docker ps
#启动成功，可以看到容器运行的详细信息
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                 NAMES
3ad7182aa47f        sshd:ubuntu         "/run.sh"           2 seconds ago       Up 2 seconds        0.0.0.0:100->22/tcp   focused_ptolemy
> ssh 192.168.1.200 -p 100
#在刚才复制公钥的机器上登陆容器
The authenticity of host '[192.168.1.200]:100 ([192.168.1.200]:100)' can't be established.
ECDSA key fingerprint is 5f:6e:4c:54:8f:c7:7f:32:c2:38:45:bb:16:03:c9:e8.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[192.168.1.200]:100' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 14.04 LTS (GNU/Linux 3.2.0-37-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@3ad7182aa47f:~#
#成功登陆，镜像创建成功。

run.sh 脚本内容

#!/bin/bash
/usr/sbin/sshd -D

Dockerfile 的基础知识，在 1.8 章节讲过，下面我们就介绍下如何使用 Dockerfile 来完成上一节的操作。

创建文件夹

首先，创建一个叫做 sshd_ubuntu 的文件夹，用于存放我们的 Dockerfile 、脚本文件、以及其他文件。

$ mkdir sshd_ubuntu
$ ls
sshd_ubuntu
$ cd sshd_ubuntu/
$ touch Dockerfile run.sh
$ ls
Dockerfile  run.sh

编写 shell 脚本和 authorized_keys 文件

其中脚本文件 run.sh 的内容与上一小节一致

#!/bin/bash
/usr/sbin/sshd -D

创建 authorized_keys 文件

$ ssh-keygen
#根据提示生成访问密钥
$ cat ~/.ssh/id_rsa.pub >authorized_keys
#复制公钥到 authorized_keys 文件中

下面是 Dockerfile 的内容及解释

#设置继承镜像
FROM ubuntu:14.04
#提供一些作者的信息
MAINTAINER dwj_zz@163.com
#下面开始运行命令,此处更改ubuntu的源为国内163的源
RUN echo "deb http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse" > /etc/apt/sources.list
RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse" >> /etc/apt/sources.list
RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse" >> /etc/apt/sources.list
RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse" >> /etc/apt/sources.list
RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse" >> /etc/apt/sources.list
RUN apt-get update

#安装 ssh 服务
RUN apt-get install -y openssh-server
RUN mkdir -p /var/run/sshd
RUN mkdir -p /root/.ssh
#取消pam限制
RUN sed -ri 's/session    required     pam_loginuid.so/#session    required     pam_loginuid.so/g' /etc/pam.d/sshd

#复制配置文件到相应位置,并赋予脚本可执行权限
ADD authorized_keys /root/.ssh/authorized_keys
ADD run.sh /run.sh
RUN chmod 755 /run.sh

#开放端口
EXPOSE 22

#设置自启动命令
CMD ["/run.sh"]

创建镜像

$ sudo docker build -t sshd:dockerfile .
Sending build context to Docker daemon 5.632 kB
Sending build context to Docker daemon
Step 0 : FROM ubuntu:14.04
^Z
[1]+  Stopped                 sudo docker build -t sshd:dockerfile .
#这里我发现创建的速度好慢，于是暂停创建过程，先查看下本地 images
$ sudo docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
sshd                ubuntu              7aef2cd95fd0        12 hours ago        255.2 MB
busybox             latest              e72ac664f4f0        3 weeks ago         2.433 MB
ubuntu              latest              ba5877dc9bec        3 months ago        192.7 MB
#原来我们的 ubuntu 镜像是使用默认的 latest 标签，而我们在 Dockerfile 中一般都是指定版本标签。
$ sudo docker tag ba5 ubuntu:14.04
$ pwd
/home/xxx/sshd_ubuntu
$ sudo docker build -t sshd:dockerfile .
#这里注意一下，在最后还有一个 “.” ，表示使用当前目录的 Dockerfile
Sending build context to Docker daemon 5.632 kB
Sending build context to Docker daemon
Step 0 : FROM ubuntu:14.04
 ---> ba5877dc9bec
Step 1 : MAINTAINER dwj_zz@163.com
 ---> Running in 188d74d02d35
 ---> 473eb019b331
Removing intermediate container 188d74d02d35
#使用 Dockerfile 创建，他会帮你删除中间无用的文件层
Step 2 : RUN echo "deb http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse" > /etc/apt/sources.list
 ---> Running in f52e2a583db5
 ---> bd4ceef2ee19
Removing intermediate container f52e2a583db5
Step 3 : RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse" >> /etc/apt/sources.list
 ---> Running in 897d65dfe9be
 ---> 9cd736f11928
Removing intermediate container 897d65dfe9be
Step 4 : RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse" >> /etc/apt/sources.list
 ---> Running in ec3433db813e
 ---> 3fca0b605de4
Removing intermediate container ec3433db813e
Step 5 : RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse" >> /etc/apt/sources.list
 ---> Running in 4a0fe165598f
 ---> f6d1c7af36c8
Removing intermediate container 4a0fe165598f
Step 6 : RUN echo "deb http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse" >> /etc/apt/sources.list
 ---> Running in 209179c21053
 ---> 0cda758c9f3c
Removing intermediate container 209179c21053
Step 7 : RUN apt-get update
 ---> Running in 1fd40eb66f7b
Ign http://archive.ubuntu.com trusty-proposed InRelease
Get:1 http://archive.ubuntu.com trusty-proposed Release.gpg [933 B]
Get:2 http://archive.ubuntu.com trusty-proposed Release [110 kB]
Get:3 http://archive.ubuntu.com trusty-proposed/main amd64 Packages [160 kB]
...
#为了节约篇幅，删去一些无关紧要的内容
Fetched 11.3 MB in 1min 37s (116 kB/s)
Reading package lists...
 ---> 0f132591eddc
Removing intermediate container 1fd40eb66f7b
Step 8 : RUN apt-get install -y openssh-server
 ---> Running in 399e4ea726d2
Reading package lists...
Building dependency tree...
Reading state information...
The following extra packages will be installed:
  ca-certificates krb5-locales libck-connector0 libedit2 libgssapi-krb5-2
  libidn11 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib libwrap0 libx11-6
  libx11-data libxau6 libxcb1 libxdmcp6 libxext6 libxmuu1 ncurses-term
  openssh-client openssh-sftp-server openssl python python-chardet
  python-minimal python-requests python-six python-urllib3 python2.7
  python2.7-minimal ssh-import-id tcpd wget xauth
Suggested packages:
  krb5-doc krb5-user ssh-askpass libpam-ssh keychain monkeysphere rssh
  molly-guard ufw python-doc python-tk python2.7-doc binutils binfmt-support
The following NEW packages will be installed:
  ca-certificates krb5-locales libck-connector0 libedit2 libgssapi-krb5-2
  libidn11 libk5crypto3 libkeyutils1 libkrb5-3 libkrb5support0
  libpython-stdlib libpython2.7-minimal libpython2.7-stdlib libwrap0 libx11-6
  libx11-data libxau6 libxcb1 libxdmcp6 libxext6 libxmuu1 ncurses-term
  openssh-client openssh-server openssh-sftp-server openssl python
  python-chardet python-minimal python-requests python-six python-urllib3
  python2.7 python2.7-minimal ssh-import-id tcpd wget xauth
0 upgraded, 38 newly installed, 0 to remove and 29 not upgraded.
Need to get 7599 kB of archives.
After this operation, 35.3 MB of additional disk space will be used.
Get:1 http://mirrors.163.com/ubuntu/ trusty/main libedit2 amd64 3.1-20130712-2 [86.7 kB]
...
Running hooks in /etc/ca-certificates/update.d....done.
Processing triggers for ureadahead (0.100.0-16) ...
 ---> 62f952643e33
Removing intermediate container 399e4ea726d2
Step 9 : RUN mkdir -p /var/run/sshd
 ---> Running in aa1c4d469284
 ---> e81557dd4887
Removing intermediate container aa1c4d469284
Step 10 : RUN mkdir -p /root/.ssh
 ---> Running in 0626987081d0
 ---> 23882ee06756
Removing intermediate container 0626987081d0
Step 11 : RUN sed -ri 's/session    required     pam_loginuid.so/#session    required     pam_loginuid.so/g' /etc/pam.d/sshd
 ---> Running in 3808c650bf85
 ---> 6c0ca1d20d7f
Removing intermediate container 3808c650bf85
Step 12 : ADD authorized_keys /root/.ssh/authorized_keys
 ---> a64bbd8ae617
Removing intermediate container 16e2d93d6ef0
Step 13 : ADD run.sh /run.sh
 ---> 230711022f7d
Removing intermediate container 137e56188d7b
Step 14 : RUN chmod 755 /run.sh
 ---> Running in a876e4ea378e
 ---> 32d74bbb7406
Removing intermediate container a876e4ea378e
Step 15 : EXPOSE 22
 ---> Running in eeaf9352ca11
 ---> 901e3fa9f596
Removing intermediate container eeaf9352ca11
Step 16 : CMD /run.sh
 ---> Running in 48c37db83ffb
 ---> 570c26a9de68
Removing intermediate container 48c37db83ffb
Successfully built 570c26a9de68
#最后，返回告诉我们创建成功，镜像 id 号是570c26a9de68，让我们来查看下
$ sudo docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
sshd                dockerfile          570c26a9de68        4 minutes ago       246.5 MB
sshd                ubuntu              7aef2cd95fd0        12 hours ago        255.2 MB
busybox             latest              e72ac664f4f0        3 weeks ago         2.433 MB
ubuntu              14.04               ba5877dc9bec        3 months ago        192.7 MB
ubuntu              latest              ba5877dc9bec        3 months ago        192.7 MB

测试镜像，运行容器

我们使用刚才我们创建的 sshd:dockerfile 来运行一个容器，看看时候达到我们的要求。

$ sudo docker ps
#这是上一小节，我们用 ”commit“ 方式建立的容器
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                 NAMES
3ad7182aa47f        sshd:ubuntu         "/run.sh"           12 hours ago        Up 3 seconds        0.0.0.0:100->22/tcp   focused_ptolemy
$ sudo docker run -d -p 101:22 sshd:dockerfile
#注意到，跟上一小节运行的容器的命令不一样，不需要在输入命令‘/run.sh’了，因为已经在 Dockerfile 中定义了自启动命令。
890c04ff8d769b604386ba4475253ae8c21fc92d60083759afa77573bf4e8af1
$ sudo docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS                 NAMES
890c04ff8d76        sshd:dockerfile     "/run.sh"           4 seconds ago       Up 3 seconds        0.0.0.0:101->22/tcp   high_albattani
3ad7182aa47f        sshd:ubuntu         "/run.sh"           12 hours ago        Up 28 seconds       0.0.0.0:100->22/tcp   focused_ptolemy

在本地新开一个终端，连接到新建的容器

> ssh 192.168.1.200 -p 101
The authenticity of host '[192.168.1.200]:101 ([192.168.1.200]:101)' can't be established.
ECDSA key fingerprint is d1:59:f1:09:3b:09:79:6d:19:16:f4:fd:39:1b:be:27.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[192.168.1.200]:101' (ECDSA) to the list of known hosts.
Welcome to Ubuntu 14.04 LTS (GNU/Linux 3.2.0-37-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@890c04ff8d76:~#
测试成功

其实，在社区中，对于是否需要为 docker 容器一直有争论。

• 一方的观点是：docker 在声明中有一个的理念是一个容器运行一个服务，如果每个容器都运行一个 ssh 服务，就违背了这个理念，另外他们认为根本没有从远程主机进入容器进行维护的必要。

• 另一方的观点是：在 1.3 版本之前，如果要用 attach 进入容器，经常容易出现卡死的情况，1.3 之后，官方推出了 docker exec工具，在从宿主主机进入是没有障碍了，但是如果要从其他远程主机进入容器依然没有更好的解决方案。

通 过一些目前看来较为复杂的方式确实能够不需要进入容器进行维护，但是使用 ssh 进行服务器的维护，是目前 linux 管理员熟悉的方式，在 docker 推出更加高效、安全的方式对容器进行维护之前，目前容器的 ssh 服务还是比较重要的，而且它对资源的占用，并没想象中的大。