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