1, the concept of
Dockerfile is a text file which contains the instructions and parameters of rows, each row of a layer of build instructions, and therefore each line of instructions is to describe how the layer should be constructed; they greatly simplifies the process from start to finish deployment; Dockerfile from fROM command to start, followed by followers of the various methods, commands and parameters, and the final output image can be used to create a new container.
2, command Detailed
instruction |
description |
Examples |
FROM |
Must be the first command, specify the base image |
FROM centos:latest |
MAINTAINER |
This command is used to declare the author, should be placed FROM the next line |
MAINTAINER wzs |
RUN |
Construction executed when the mirror shell command is Dockerfile core of the execution of the command;
|
RUN yun install httpd RUN [“yum”,”install ”,”httpd”] |
CMD |
With the RUN command similar, execute shell commands; and RUN difference is, RUN executed in the process of building the mirror, CMD is called after building a container with a mirror; if we docker run specified command or when there EntryPoint , then CMD will be covered; Dockerfile multiple CMD command only the last one will |
Use one: without the brackets CMD echo "hello cmd!" Usage II: with brackets, without any default shell CMD ["/bin/bash", "-c", "echo 'hello cmd!'"] Use three: pass arguments to the ENTRYPOINT CMD [“-l”] |
ENTRYPOINT |
And CMD commands, the execution time is running container shell command; and CMD difference is, CMD can perform docker run the specified command covering the time, ENTRYPOINT only use --entrypoint to cover; CMD and ENTRYPOINT can be used with, ENTRYPOINT used as fixed command, CMD used ENTRYPOINT variable parameters in order to carry |
Use one: do not use [] any run and CMD is not to be passed, it will cover the CMD ENTRYPOINT /bin/bash -c ‘start.sh’ Usage II: Use [] can be passed CMD the -l parameter, i.e., ls -l CMD [“-l”] ENTRYPOINT [“ls”] |
EXPOSE |
Exposed container port; you can also specify a port is listening on TCP or UDP , the default is TCP |
EXPOSE 80,443 EXPOSE 80/udp |
ENV |
Setting environment variables within the container , you can start the container --env <key> = <value> modified values environment variable |
ENV MYSQL_ROOT_PASSWD 123456 |
ADD |
Copy files or directories to the mirror, if it is URL or compression or decompression package will automatically download |
ADD https://xxx.com/html.tar.gz / var / www / html ADD html.tar.gz / var / www / html |
COPY |
Copy the file or directory to the mirror |
COPY ./test.txt /tmp/test.txt |
USER |
To RUN , CMD , EntryPoint , COPY , the ADD specify run user to execute commands |
USER wzs |
WORKDIR |
为RUN、CMD、ENTRYPOINT、COPY、ADD设置工作目录 |
WORKDIR /data |
ARG |
在构建镜像时指定一些参数 |
ARG user USER $user |
3、CMD和ENTRYPOINT用法讲解
说明：因CMD和ENTRYPOINT的用法比较复杂，这里举几个案例对CMD、ENTRYPOINT的区别和用法进行解读
案例一：CMD用法1
docker build -t cmd:v1 -f /var/Dockerfile/cmd-1.txt /var/Dockerfile/
使用Dockerfile构建cmd:v1镜像后，执行docke run cmd:v1可以看到使用了Dockfile中的CMD echo “123” 命令
执行docke run cmd:v1 echo “abc” 会将Dockfile中的CMD命令覆盖
案例二：CMD用法2
docker build -t cmd:v2 -f /var/Dockerfile/cmd-2.txt /var/Dockerfile/
使用[]中括号方式；这时，命令没有再任何shell终端环境下，如果我们要执行shell，必须把shell加入到中括号的参数中
执行docker run cmd:v2 ls /tmp/ 会将Dockfile中的CMD命令覆盖
案例三：CMD用法3，ENTRYPOINT用法1
CMD的第三种用法用于传参，不携带任何命令；所以要配合ENTRYPOINT使用
Dockefile文件中ENTRYPOINT中的echo 作为命令，CMD的 “hello cmd”作为传参，执行后如下：
也可以在docker run时携带参数 “hello entrypoint” 覆盖CMD的内容
案例四：CMD用法3，ENTRYPOINT用法2
当Dockerfile中的ENTRYPOINT不使用中括号后，会覆盖CMD的内容；docker run只会执行ENTRYPOINT
docker run时携带任何参数或命令都无法被传入到entrypoint里
4、实战案例
案例一、tomcat部署
首先创建一个制定tomcat镜像的目录，存放镜像所需的安装包和Dockerfile文件
Dockerfile文件内容
#使用基础镜像
FROM centos:latest
#注明作者
MAINTAINER wzs
#创建目录
RUN mkdir -p /usr/local
#添加安装包到镜像
ADD apache-tomcat-7.0.93.tar.gz /usr/local/
ADD jdk-8u221-linux-x64.tar.gz /usr/local/
#定义环境变量
ENV JAVA_HOME /usr/local/jdk1.8.0_221
ENV JRE_HOME $JAVA_HOME/jre
ENV CATALINA_HOME /usr/local/apache-tomcat-7.0.93
ENV PATH $CATALINA_HOME/bin:$JAVA_HOME/bin:$JRE_HOME/bin:$PATH
#暴露端口
EXPOSE 8080
#启动时运行tomcat进程
CMD ["/usr/local/apache-tomcat-7.0.93/bin/catalina.sh","run"]
使用Dockerfile构建镜像
docker build -t tomcat:v1 -f ./Dockfile.txt ./
使用镜像创建并运行容器
docker run -itd --name tomcat-docker -p 8081:8080 tomcat:v1
案例二、nginx部署
创建一个制定nginx镜像的目录，存放镜像所需的安装包和Dockerfile文件
Dockerfile文件内容
#使用基础镜像
FROM centos:latest
#声明作者
MAINTAINER wzs
#安装依赖库
RUN yum -y install gcc gcc-c++ make pcre-devel zlib-devel openssh-devel zlib
#添加安装包到镜像
ADD nginx-1.8.0.tar.gz /usr/local
#编译部署
RUN cd /usr/local/nginx-1.8.0 && \
./configure --prefix=/usr/local/nginx && \
make && \
make install
#删除安装包文件
RUN rm -rf /usr/local/nginx-1.8.0
#暴露端口
EXPOSE 80
#定义工作目录
WORKDIR /usr/local/nginx
#启动时运行nginx
CMD ["./sbin/nginx","-g","daemon off;"]
使用Dockerfile文件构建镜像
docker build -t nginx:v1 -f ./Dockerfile.txt ./
使用镜像创建运行容器
docker run -itd --name nginx-docker -p 81:80 nginx:v1
案例三、mysql部署
创建一个制定tomcat镜像的目录，因为mysql使用yum安装；所以这里只有Dockerfile文件
Dockerfile文件内容
#使用基础镜像
FROM centos:latest
#作者
MAINTAINER wzs
#添加mysql用户
RUN useradd -d /opt/mysql mysql
#下载mysql的yum安装包文件
ADD http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm /opt/
RUN rpm -ivh /opt/mysql-community-release-el7-5.noarch.rpm
#安装mysql-server
RUN yum install -y mysql-server
#mysql初始化
RUN mysql_install_db --user=mysql --basedir=/usr/ --ldata=/var/lib/mysql/
#暴露端口
EXPOSE 3306
#这里使用CMD和ENTRYPOINT组合，ENTRYPOINT中为mysql服务启动的固定命令，CMD指定mysql的运行用户，所在docker run时可以覆盖修改
CMD ["--user=mysql"]
ENTRYPOINT ["/usr/sbin/mysqld"]
使用Dockerfile构建mysql镜像
docker build -t mysql:v1 -f ./Dockerfile ./
使用镜像创建运行容器
docker run -itd --name mysql-docker mysql:v1
