Docker定制容器镜像的2种方法（推荐）

原作者: [db:作者] 来自: [db:来源] 收藏邀请

一、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。

二、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

2.启动容器并进行配置

启动容器，

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

[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

[root@docker ~]# docker exec centos_7.0-1 hostname -i
172.17.0.4

[root@docker ~]# ssh [email protected]
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.
[email protected]'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）

我的认为它就像ansible的playbook一样。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:latest

MAINTAINER 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>:<tag>. 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 Resolution

Dependencies Resolved

================================================================================
 Package       Arch   Version            Repository Size
================================================================================
Installing:
 net-tools      x86_64  2.0-0.17.20131004git.el7    base    304 k
 openssh-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 k
 fipscheck-lib    x86_64  1.4.1-5.el7          base    11 k
 openssh       x86_64  6.6.1p1-25.el7_2        updates  435 k
 tcp_wrappers-libs  x86_64  7.6-77.el7           base    66 k

Transaction 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) <[email protected]>"
 Fingerprint: 6341 ab27 53d7 8a78 a7c2 7bb1 24c6 a8a7 f4a8 0eb5
 Package  : 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 transaction
 Installing : 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

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 [email protected]
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.
[email protected]'s password: 
[root@7ae51091c138 ~]# w
 11:19:34 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。上述就是定义镜像的两种方式，如果还有其它更为方便的还望不吝赐教哈。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持极客世界。