创建镜像三种方法
Docker镜像创建方法有三种，分别为基于已有镜像创建、基于本地模板创建以及基于Dockerfile创建。
通过Dockerfile创建镜像
这里主要记录下基于Dockerfile创建方法，Dockerfile是由一组指令组成的文件，其中每条指令对应Linux中的一条命令，Docker程序将读取Dockerfile中的指令生成指定镜像。
Dockerfile结构大致分为四个部分：基础镜像信息、维护者信息、镜像操作指令和容器启动时执行指令 。Dockerfile每行支持一条指令，每条指令可带多个参数，支持使用以#号开头的注释。
Docker操作指令
| 指令 |
含义 |
| FROM镜像 |
指定新镜像所基于的镜像，必须为第一条指令 |
| MAINTAINER 名字 |
新镜像的维护人信息 |
| RUN 命令 |
在所基于的镜像上执行命令，并提交到新镜像中 |
| EXPOSE端口号 |
指定新镜像加载到Docker时开启的端口号 |
| ENV 环境变量 变量值 |
设置一个环境变量的值，会被后面的RUN使用 |
| ADD 源文件/目录 目标文件/目录 |
将源文件复制到目标文件，源文件要与Docker位于同一目录下，或者为一个URL |
| COPY 源文件/目录 目标文件/目录 |
将本地主机上的源文件/目录复制到目标地点，源文件/目录要与Dockerfile在同一目录下 |
| VOLUME["目录"] |
在容器中创建一个挂载点 |
| USER 用户名 /UID |
指定运行容器时的用户 |
| WORKDIR 路径 |
为后续的RUN、CMD、ENTRYPOINT指定工作目录 |
| ONBUILD命令 |
指定所生成的镜像作为一个基础镜像时所要运行的命令 |
| CMD["要运行的程序"，"参数1"，"参数2"] |
指定启动容器时运行的命令或脚本，只能有一条CMD命令，多条时只有最后一条被执行 |
以下通过Dockerfile来创建httpd镜像
1.创建镜像工作目录并进入
mkdir apache
cd apache/
2.创建并编写dockerfile文件
vim Dockerfile
#基于centos镜像
FROM centos
#维护人的信息
MAINTAINER The CentOS Project <303323496@qq.com>
#安装httpd软件包
RUN yum -y update
RUN yum -y install httpd
#开启80端口
EXPOSE 80
#复制网站首页文件至镜像中web站点下
ADD index.html /var/www/html/index.html
#复制该脚本至镜像中，并修改其权限
ADD run.sh /run.sh
RUN chmod 775 /run.sh
#当启动容器时执行的脚本文件
CMD ["/run.sh"]
![通过Dockerfile创建docker镜像]()
3.创建脚本文件
vim run.sh
#!/bin/bash
#清空httpd缓存文件
rm -rf /run/httpd/*
#启动httpd服务
exec /usr/sbin/apachectl -D FOREGROUND
4.创建网站首页文件
echo "Thiss is Nginx webapp." > index.html
5.查看当前目录文件列表
ls
![通过Dockerfile创建docker镜像]()
6.通过Dockerfile文件生成镜像
docker build -t httpd:centos .
Sending build context to Docker daemon 4.096kB
Step 1/9 : FROM centos
---> 5182e96772bf
Step 2/9 : MAINTAINER The CentOS Project <303323496@qq.com>
---> Running in 6d7c8eae519d
---> 46fc589066ff
Removing intermediate container 6d7c8eae519d
Step 3/9 : RUN yum -y update
---> Running in 444105af6041
Loaded plugins: fastestmirror, ovl
Determining fastest mirrors
* base: mirrors.zju.edu.cn
* extras: mirrors.zju.edu.cn
* updates: mirrors.cn99.com
Resolving Dependencies
--> Running transaction check
---> Package centos-release.x86_64 0:7-5.1804.1.el7.centos will be updated
---> Package centos-release.x86_64 0:7-5.1804.4.el7.centos will be an update
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Updating:
centos-release x86_64 7-5.1804.4.el7.centos updates 25 k
Transaction Summary
================================================================================
Upgrade 1 Package
Total download size: 25 k
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
Public key for centos-release-7-5.1804.4.el7.centos.x86_64.rpm is not installed
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
warning: /var/cache/yum/x86_64/7/updates/packages/centos-release-7-5.1804.4.el7.centos.x86_64.rpm:Header V3 RSA/SHA256 Signature, key ID f4a80eb5: NOKEY
Importing GPG key 0xF4A80EB5:
Userid : "CentOS-7 Key (CentOS 7 Official Signing Key) <security@centos.org>"
Fingerprint: 6341 ab27 53d7 8a78 a7c2 7bb1 24c6 a8a7 f4a8 0eb5
Package : centos-release-7-5.1804.1.el7.centos.x86_64 (@Updates)
From : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Updating : centos-release-7-5.1804.4.el7.centos.x86_64 1/2
Cleanup : centos-release-7-5.1804.1.el7.centos.x86_64 2/2
Verifying : centos-release-7-5.1804.4.el7.centos.x86_64 1/2
Verifying : centos-release-7-5.1804.1.el7.centos.x86_64 2/2
Updated:
centos-release.x86_64 0:7-5.1804.4.el7.centos
Complete!
---> 8a4bb67da908
Removing intermediate container 444105af6041
Step 4/9 : RUN yum -y install httpd
---> Running in 982f008f5f3c
Loaded plugins: fastestmirror, ovl
Loading mirror speeds from cached hostfile
* base: mirrors.zju.edu.cn
* extras: mirrors.zju.edu.cn
* updates: mirrors.cn99.com
Resolving Dependencies
--> Running transaction check
---> Package httpd.x86_64 0:2.4.6-80.el7.centos.1 will be installed
--> Processing Dependency: httpd-tools = 2.4.6-80.el7.centos.1 for package: httpd-2.4.6-80.el7.centos.1.x86_64
--> Processing Dependency: system-logos >= 7.92.1-1 for package: httpd-2.4.6-80.el7.centos.1.x86_64
--> Processing Dependency: /etc/mime.types for package: httpd-2.4.6-80.el7.centos.1.x86_64
--> Processing Dependency: libaprutil-1.so.0()(64bit) for package: httpd-2.4.6-80.el7.centos.1.x86_64
--> Processing Dependency: libapr-1.so.0()(64bit) for package: httpd-2.4.6-80.el7.centos.1.x86_64
--> Running transaction check
---> Package apr.x86_64 0:1.4.8-3.el7_4.1 will be installed
---> Package apr-util.x86_64 0:1.5.2-6.el7 will be installed
---> Package centos-logos.noarch 0:70.0.6-3.el7.centos will be installed
---> Package httpd-tools.x86_64 0:2.4.6-80.el7.centos.1 will be installed
---> Package mailcap.noarch 0:2.1.41-2.el7 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
httpd x86_64 2.4.6-80.el7.centos.1 updates 2.7 M
Installing for dependencies:
apr x86_64 1.4.8-3.el7_4.1 base 103 k
apr-util x86_64 1.5.2-6.el7 base 92 k
centos-logos noarch 70.0.6-3.el7.centos base 21 M
httpd-tools x86_64 2.4.6-80.el7.centos.1 updates 90 k
mailcap noarch 2.1.41-2.el7 base 31 k
Transaction Summary
================================================================================
Install 1 Package (+5 Dependent packages)
Total download size: 24 M
Installed size: 31 M
Downloading packages:
--------------------------------------------------------------------------------
Total 1.1 MB/s | 24 MB 00:21
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : apr-1.4.8-3.el7_4.1.x86_64 1/6
Installing : apr-util-1.5.2-6.el7.x86_64 2/6
Installing : httpd-tools-2.4.6-80.el7.centos.1.x86_64 3/6
Installing : centos-logos-70.0.6-3.el7.centos.noarch 4/6
Installing : mailcap-2.1.41-2.el7.noarch 5/6
Installing : httpd-2.4.6-80.el7.centos.1.x86_64 6/6
Verifying : mailcap-2.1.41-2.el7.noarch 1/6
Verifying : httpd-tools-2.4.6-80.el7.centos.1.x86_64 2/6
Verifying : apr-util-1.5.2-6.el7.x86_64 3/6
Verifying : httpd-2.4.6-80.el7.centos.1.x86_64 4/6
Verifying : apr-1.4.8-3.el7_4.1.x86_64 5/6
Verifying : centos-logos-70.0.6-3.el7.centos.noarch 6/6
Installed:
httpd.x86_64 0:2.4.6-80.el7.centos.1
Dependency Installed:
apr.x86_64 0:1.4.8-3.el7_4.1
apr-util.x86_64 0:1.5.2-6.el7
centos-logos.noarch 0:70.0.6-3.el7.centos
httpd-tools.x86_64 0:2.4.6-80.el7.centos.1
mailcap.noarch 0:2.1.41-2.el7
Complete!
---> d3f0d6f963cb
Removing intermediate container 982f008f5f3c
Step 5/9 : EXPOSE 80
---> Running in b511725feca7
---> 7f7887f5875e
Removing intermediate container b511725feca7
Step 6/9 : ADD index.html /var/www/html/index.html
---> 3c5953c9fd43
Removing intermediate container 85dad653f265
Step 7/9 : ADD run.sh /run.sh
---> 41980651502b
Removing intermediate container 91ff7e24daa4
Step 8/9 : RUN chmod 775 /run.sh
---> Running in 7aebb5d8f194
---> f673460e23c7
Removing intermediate container 7aebb5d8f194
Step 9/9 : CMD /run.sh
---> Running in 9c0f5c4f1e32
---> 551b9fc524ba
Removing intermediate container 9c0f5c4f1e32
Successfully built 551b9fc524ba
Successfully tagged httpd:centos
7.镜像文件加载到容器中运行
docker run -d -p 80:80 --name=httpd httpd:centos
![通过Dockerfile创建docker镜像]()
![通过Dockerfile创建docker镜像]()
8.查看运行中的容器
docker ps
![通过Dockerfile创建docker镜像]()
9.运行浏览器测试httpd服务
http://192.168.96.44:80
![通过Dockerfile创建docker镜像]()
![通过Dockerfile创建docker镜像]()
