DockerFile简明教程

需求

由于在测试环境中使用了docker官网的centos 镜像，但是该镜像里面默认没有安装ssh服务，在做测试时又需要开启ssh。所以上网也查了查资料。下面详细的纪录下。在centos 容器内安装ssh后，转成新的镜像用于后期测试使用。

镜像定制

第一种方式（手动修改容器镜像）

1.先下载centos镜像

[root@docker ~]# docker pull centos:7

2.启动容器并进行配置

启动容器，

[root@docker ~]# docker run -it -d --name test-centos1 centos:7
d72250ecaa5e3e36226a1edd749f494d9f00eddc4143c81ac3565aa4e551791a

命令注释：-it :　进行交互式操作

-d :　等同于 -d=true,容器将会在后台运行，不然执行一次命令后，退出后，便是exit状态了。

–name : 容器启动后的名字，默认不指定，将会随机产生一个名字。或者使用 -name=“containers_name”

centos：使用的镜像名称

进入容器，安装ssh server，以及配置开机启动

[root@docker ~]# docker exec -it test-centos1 /bin/bash
[root@d72250ecaa5e /]# ifconfig
bash: ifconfig: command not found

注：命令最后参数 /bin/bash： 指进入容器时执行的命令（command）
我们检查了下容器，暂时安装以下必用的软件吧 net-tools，openssh-server

[root@d72250ecaa5e /]# yum install openssh-server net-tools -y

创建ssh 所需的目录，并在根目录创建sshd 启动脚本，输入/usr/sbin/sshd -D

[root@d72250ecaa5e /]# mkdir -pv /var/run/sshd
mkdir: created directory '/var/run/sshd'
[root@d72250ecaa5e /]# cat /auto_sshd.sh 
#!/bin/bash
/usr/sbin/sshd -D
[root@d72250ecaa5e /]# chmod +x /auto_sshd.sh

修改容器内root 的账户密码

[root@d72250ecaa5e /]# echo "root:iloveworld" | chpasswd 

生成ssh 主机dsa 密钥（不然ssh 该容器时，会出现错误。

[root@d72250ecaa5e /]# ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key
[root@d72250ecaa5e /]# ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key

我们加一个history记录的时间功能吧，这样方便后期查看

echo 'export HISTTIMEFORMAT="%F %T `whoami` "' >> /etc/profile

OK，配置基本完毕咯。清理命令历史纪录，之后退出容器。现在可以生成一个新的docker 镜像了。
3.配置完成后，进行打包成新的镜像

[root@docker ~]# docker commit test-centos1 centos_sshd:7.0
sha256:6e3330b30dfff5f029f102874e54cfffffbc37dcf2a4eb7304c817148fbc944d
[root@docker ~]# docker images
REPOSITORY                   TAG                 IMAGE ID            CREATED             SIZE
centos_sshd                  7.0                 6e3330b30dff        8 seconds ago       310.1 MB
docker.io/ubuntu             latest              e4415b714b62        12 days ago         128.1 MB

命令注释：commit： 提交一个具有新配置的容器成为镜像，后面跟容器的name 或者容器Id ，最后是生成新镜像的名字

更新：这条命令更方便以后启动，如下：

[root@docker ~]# docker commit --change='CMD ["/auto_sshd.sh"]' -c "EXPOSE 22" test-centos1 centos_sshd:7.0
sha256:7bb4efd82c4ff1f241cbc57ee45aab1b05d214b1e9fcd51196696c67d480e70b

命令注释： --change : 将后期使用此镜像运行容器时的命令参数、开放的容器端口提前设置好。

4.验证

查看镜像，并启动新的容器

[root@docker ~]# docker images
REPOSITORY                   TAG                 IMAGE ID            CREATED             SIZE
centos_sshd                  7.0                 7bb4efd82c4f        4 minutes ago       310.1 MB
docker.io/ubuntu             latest              e4415b714b62        12 days ago         128.1 MB[root@docker ~]# docker run -d -it --name centos_7.0-1 centos_sshd:7.0
ec17e553d5c4c60865afeb99df8dfd1f4e7d4ba6e1b0d5516f9127f09d1d6356
[root@docker ~]# docker ps -a
CONTAINER ID        IMAGE                     COMMAND                  CREATED             STATUS           PORTS          NAMES
ec17e553d5c4        centos_sshd:7.0           "/auto_sshd.sh"          6 seconds ago       Up 5 seconds     22/tcp         centos_7.0-1

进行ssh测试，先查看一下该容器的ip，之后ssh。ok，密码使用前面设置的iloveworld

[root@docker ~]# docker exec centos_7.0-1 hostname -i
172.17.0.4[root@docker ~]# ssh root@172.17.0.4
The authenticity of host '172.17.0.4 (172.17.0.4)' can't be established.
RSA key fingerprint is 87:88:07:12:ac:0a:90:28:10:e1:9e:eb:1f:d6:c9:9d.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '172.17.0.4' (RSA) to the list of known hosts.
root@172.17.0.4's password: 
Last login: Tue Nov 29 16:00:49 2016 from gateway[root@ec17e553d5c4 ~]# w   16:34:17 up 63 days,  7:49,  1 user,  load average: 0.00, 0.02, 0.05
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    gateway          16:34    1.00s  0.00s  0.00s w
[root@ec17e553d5c4 ~]# ping gateway
PING gateway (172.17.0.1) 56(84) bytes of data.
64 bytes from gateway (172.17.0.1): icmp_seq=1 ttl=64 time=0.048 ms

第二种方式（推荐：利用Dockerfile文件）

Dockerfile包含创建镜像所需要的全部指令。基于在Dockerfile中的指令，我们可以使用Docker build命令来创建镜像。通过减少镜像和容器的创建过程来简化部署。

1.创建Dockerfile文件

新建一个目录，在里面新建一个dockerfile文件（新建一个的目录，主要是为了和以防和其它dockerfile混乱 ）

[root@docker ~]# mkdir centos7-dockerfile[root@docker centos7-dockerfile]# cat Dockerfile 
# The dockerfile has Change add sshd services on Centos7.0
#centos7:latest image
FROM centos:7MAINTAINER Yifeng,http://www.cnblogs.com/hanyifeng#Install sshd net-tools
RUN yum install openssh-server net-tools -y
RUN mkdir /var/run/sshd#Set password for root
RUN echo 'root:iloveworld' | chpasswd
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config#Set history record
ENV HISTTIMEFORMAT "%F %T  "#Fix sshd service:Read from socket failed: Connection reset by peer?
RUN ssh-keygen -A#Change timezone CST
RUN \cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime#Open 22 port
EXPOSE 22#Auto running sshd service
CMD ["/usr/sbin/sshd","-D"]

上述文件内容就是一个dockerfile 常见的命令组合。开头带＃号的为注释

文件解释：

FROM： 必不可少的命令，从某个镜像作为基。如 FROM <image_name> ，或者 FROM <image_name>:. 如果不加tag，默认为latest。先从本地镜像仓库去搜索基镜像，如过本地没有，在去网上docker registry去寻找。

MAINTAINER：标明该Dockerfile作者及联系方式，可忽略不写

RUN：建立新的镜像时，可以执行在系统里的命令，如安装特定的软件以及设置环境变量。

ENV：设置系统环境变量（注意：写在/etc/profile里的命令在dockerfile这里会不生效，所以为改成ENV的方式）

EXPOSE：开放容器内的端口，但不和宿主机进行映射。方便在宿主机上进行开发测试。（如需映射到宿主机端口，可在运行容器时使用 -p host_port:container_port）

CMD：设置执行的命令，经常用于容器启动时指定的某个操作。如执行自定义脚本服务，或者是执行系统命令。CMD 只能存在一条，如在Dockerfile中有多条CMD的话，只有最后一条CMD生效！

2.执行build 创建镜像

使用docker build命令来创建镜像

[root@docker centos7-dockerfile]# docker build -t centos_sshd_1 .

-t 选项来docker build新的镜像以便于标记构建的镜像，. 表示当前目录，也可以指定dockerfile 文件所在目录。

下面缩略的内容是构建镜像时的输出，可以看下。

[root@docker centos7-dockerfile]# docker build -t centos_sshd_1 .
Sending build context to Docker daemon 4.096 kB
Step 1 : FROM centos:latest---> 0584b3d2cf6d
Step 2 : MAINTAINER Yifeng,http://www.cnblogs.com/hanyifeng---> Running in da643b55dc77---> 1087074d44e4
Removing intermediate container da643b55dc77
Step 3 : RUN yum install openssh-server net-tools -y---> Running in 5626d8f0f892
Loaded plugins: fastestmirror, ovl
Determining fastest mirrors* base: mirrors.btte.net* extras: mirrors.tuna.tsinghua.edu.cn* updates: mirrors.btte.net
Resolving Dependencies
--> Running transaction check
---> Package net-tools.x86_64 0:2.0-0.17.20131004git.el7 will be installed
---> Package openssh-server.x86_64 0:6.6.1p1-25.el7_2 will be installed
--> Processing Dependency: openssh = 6.6.1p1-25.el7_2 for package: openssh-server-6.6.1p1-25.el7_2.x86_64
--> Processing Dependency: fipscheck-lib(x86-64) >= 1.3.0 for package: openssh-server-6.6.1p1-25.el7_2.x86_64
--> Processing Dependency: libwrap.so.0()(64bit) for package: openssh-server-6.6.1p1-25.el7_2.x86_64
--> Processing Dependency: libfipscheck.so.1()(64bit) for package: openssh-server-6.6.1p1-25.el7_2.x86_64
--> Running transaction check
---> Package fipscheck-lib.x86_64 0:1.4.1-5.el7 will be installed
--> Processing Dependency: /usr/bin/fipscheck for package: fipscheck-lib-1.4.1-5.el7.x86_64
---> Package openssh.x86_64 0:6.6.1p1-25.el7_2 will be installed
---> Package tcp_wrappers-libs.x86_64 0:7.6-77.el7 will be installed
--> Running transaction check
---> Package fipscheck.x86_64 0:1.4.1-5.el7 will be installed
--> Finished Dependency ResolutionDependencies Resolved================================================================================Package              Arch      Version                        Repository  Size
================================================================================
Installing:net-tools            x86_64    2.0-0.17.20131004git.el7       base       304 kopenssh-server       x86_64    6.6.1p1-25.el7_2               updates    436 k
Installing for dependencies:fipscheck            x86_64    1.4.1-5.el7                    base        21 kfipscheck-lib        x86_64    1.4.1-5.el7                    base        11 kopenssh              x86_64    6.6.1p1-25.el7_2               updates    435 ktcp_wrappers-libs    x86_64    7.6-77.el7                     base        66 kTransaction Summary
================================================================================
Install  2 Packages (+4 Dependent packages)Total download size: 1.2 M
Installed size: 3.4 M
Downloading packages:
Public key for fipscheck-lib-1.4.1-5.el7.x86_64.rpm is not installed
warning: /var/cache/yum/x86_64/7/base/packages/fipscheck-lib-1.4.1-5.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID f4a80eb5: NOKEY
Public key for openssh-6.6.1p1-25.el7_2.x86_64.rpm is not installed
--------------------------------------------------------------------------------
Total                                              593 kB/s | 1.2 MB  00:02     
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
Importing GPG key 0xF4A80EB5:Userid     : "CentOS-7 Key (CentOS 7 Official Signing Key) <[e-mail]>"Fingerprint: 6341 ab27 53d7 8a78 a7c2 7bb1 24c6 a8a7 f4a8 0eb5Package    : centos-release-7-2.1511.el7.centos.2.10.x86_64 (@CentOS)From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
Running transaction check
Running transaction test
Transaction test succeeded
Running transactionInstalling : fipscheck-1.4.1-5.el7.x86_64                                 1/6 Installing : fipscheck-lib-1.4.1-5.el7.x86_64                             2/6 Installing : openssh-6.6.1p1-25.el7_2.x86_64                              3/6 Installing : tcp_wrappers-libs-7.6-77.el7.x86_64                          4/6 Installing : openssh-server-6.6.1p1-25.el7_2.x86_64                       5/6 Installing : net-tools-2.0-0.17.20131004git.el7.x86_64                    6/6 Verifying  : openssh-6.6.1p1-25.el7_2.x86_64                              1/6 Verifying  : openssh-server-6.6.1p1-25.el7_2.x86_64                       2/6 Verifying  : net-tools-2.0-0.17.20131004git.el7.x86_64                    3/6 Verifying  : tcp_wrappers-libs-7.6-77.el7.x86_64                          4/6 Verifying  : fipscheck-lib-1.4.1-5.el7.x86_64                             5/6 Verifying  : fipscheck-1.4.1-5.el7.x86_64                                 6/6 Installed:net-tools.x86_64 0:2.0-0.17.20131004git.el7                                   openssh-server.x86_64 0:6.6.1p1-25.el7_2                                      Dependency Installed:fipscheck.x86_64 0:1.4.1-5.el7       fipscheck-lib.x86_64 0:1.4.1-5.el7      openssh.x86_64 0:6.6.1p1-25.el7_2    tcp_wrappers-libs.x86_64 0:7.6-77.el7   Complete!---> 7b249ed8cb54
Removing intermediate container 5626d8f0f892
Step 4 : RUN mkdir /var/run/sshd---> Running in fc94a139d438---> ea2826eccc91
Removing intermediate container fc94a139d438
Step 5 : RUN echo 'root:iloveworld' | chpasswd---> Running in ba53283081a7---> 7ce1ddb5d9c0
Removing intermediate container ba53283081a7
Step 6 : RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config---> Running in 4112281a5bf0---> be21fb6b5b1e
Removing intermediate container 4112281a5bf0
Step 7 : ENV HISTTIMEFORMAT "%F %T  "---> Running in f2081726e403---> f3fafca42170
Removing intermediate container f2081726e403
Step 8 : RUN ssh-keygen -A---> Running in 2ca9e743dee7
ssh-keygen: generating new host keys: RSA1 RSA DSA ECDSA ED25519 ---> 1a927943bee7
Removing intermediate container 2ca9e743dee7
Step 9 : RUN \cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime---> Running in afd43cc6d4d6---> 4a0cacf6cd72
Removing intermediate container afd43cc6d4d6
Step 10 : EXPOSE 22---> Running in a03551bc3bcb---> 3af544106bf4
Removing intermediate container a03551bc3bcb
Step 11 : CMD /usr/sbin/sshd -D---> Running in f45fe5eb5561---> d4620c9949b8
Removing intermediate container f45fe5eb5561
Successfully built d4620c9949b8
docker build stdout

3.查看镜像列表，并创建容器

[root@docker centos7-dockerfile]# docker images
REPOSITORY                                     TAG                 IMAGE ID            CREATED             SIZE
centos_sshd_1                                  latest              d4620c9949b8        4 minutes ago       308.4 MB
centos_sshd                                    7.0                 7bb4efd82c4f        2 days ago          310.1 MB

我们刚刚新建的容器已经存在了，现在用它来创建容器

[root@docker centos7-dockerfile]# docker run -d -it --name centos-two centos_sshd_1
7ae51091c138d249b5e97f6957073e748db278c0f1cf856e968ca78a4aec1a5b查看容器
[root@docker centos7-dockerfile]# docker ps   
CONTAINER ID        IMAGE                    COMMAND               CREATED             STATUS              PORTS             NAMES
7ae51091c138        centos_sshd_1            "/usr/sbin/sshd -D"   16 seconds ago      Up 15 seconds       22/tcp            centos-two

👌，可以看到容器的command 就是我们之前定义启动ssh 服务的，并且开放了22端口。

现在我们在宿主机上查看下该容器的ip，然后用ssh 链接进去。

[root@docker ~]# docker exec centos-two hostname -I
172.17.0.7[root@docker ~]# ssh root@172.17.0.7
The authenticity of host '172.17.0.7 (172.17.0.7)' can't be established.
ECDSA key fingerprint is 7a:38:69:d7:5e:f4:db:e8:3c:ea:92:a4:1a:a1:7b:9a.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '172.17.0.7' (ECDSA) to the list of known hosts.
root@172.17.0.7's password: 
[root@7ae51091c138 ~]# w11:19:34 up 65 days, 18:34,  1 user,  load average: 0.01, 0.04, 0.05
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    gateway          11:19    6.00s  0.00s  0.00s w

OK。