Docker容器之Dockerfile的编写

最新推荐文章于 2025-05-15 16:26:42 发布

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最新推荐文章于 2025-05-15 16:26:42 发布

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分类专栏： Linux 文章标签： Docker容器之Dockerfile的编写

本文链接：https://blog.youkuaiyun.com/qq_42036824/article/details/88624838

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一、Dockerfile的编写

编写DockFile实现安装httpd服务

导入镜像

[root@foundation19 images]# docker load -i rhel7.tar

编写Dockerfile

[root@foundation79 docker]# pwd
/tmp/docker
[root@foundation19 docker]# vim  Dockerfile
FROM rhel7      # 源镜像是rhel7，最好将名为rhel7的镜像放在本地
COPY yum.repo /etc/yum.repo.d
RUN  rpmdb --rebuilddb && yum install -y httpd
# 执行命令安装httpd并清除yum缓存
# rpmdb 命令用于初始化和重建rpm数据库
# --rebuilddb：从已安装的包头文件，反向重建RPM数据库
EXPOSE 80    # 定义端口为80
CMD ["/usr/share/httpd","-D","FOREGROUND"]
# 打开apach服务
# -D 是全局文件/etc/sysconfig/httpd中的打开参数


[root@foundation79 docker]# vim yum.repo
[rhel7.3]
name=rhel7.3
baseurl=http://172.25.19.250/rhel7.3       ##这里是网络yum源
gpgcheck=0

封装镜像，并测试能否正常使用


[root@foundation19 docker]# docker build -t rhel7:v1 .      （注意后面 有个点表示当前目录）

[root@foundation19 ~]# docker run -d --name vm1 rhel7:v1
[root@foundation19 ~]# docker inspect vm1     ##找到IP（172.17.0.2）
[root@foundation19 ~]# cd /tmp/docker/
[root@foundation19 docker]# ls
Dockerfile  yum.repo
[root@foundation19 docker]# cat index.html 
www.westos.org
[root@foundation19 docker]# docker container cp index.html vm1:/var/www/html
[root@foundation19 docker]# curl 172.17.0.2    ##可以正常访问使用
www.westos.org

添加数据卷挂载位置（VOLUME [“var/www/html”]）


[root@foundation19 docker]# cat Dockerfile 
FROM rhel7
COPY yum.repo /etc/yum.repos.d/yum.repo
RUN rpmdb --rebuilddb 
RUN yum install -y httpd 
EXPOSE 80
VOLUME ["var/www/html"]
CMD ["/usr/sbin/httpd","-D","FOREGROUND"]

#封装镜像
[root@foundation19 docker]# docker build -t rhel7:v2 .

此时可以看到 rhel7:v2比 rhel7:v1多了一层


[root@foundation19 docker]# docker history rhel7:v1 
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
a7655594dff3        About an hour ago   /bin/sh -c #(nop)  CMD ["/usr/sbin/httpd" "-…   0B                  
2fb76a304e03        About an hour ago   /bin/sh -c #(nop)  EXPOSE 80                    0B                  
ec1a73b2e7d6        About an hour ago   /bin/sh -c yum install -y httpd                 52.8MB              
031f7a8b74a0        About an hour ago   /bin/sh -c rpmdb --rebuilddb                    6.64MB              
c32fc667b5f3        About an hour ago   /bin/sh -c #(nop) COPY file:254d80ba480dfa06…   71B                 
0a3eb3fde7fd        4 years ago                                                         140MB               Imported from -
[root@foundation19 docker]# docker history rhel7:v2
IMAGE               CREATED             CREATED BY                                      SIZE                COMMENT
3d3de7d12c6c        38 seconds ago      /bin/sh -c #(nop)  CMD ["/usr/sbin/httpd" "-…   0B                  
ab058c45bd94        39 seconds ago      /bin/sh -c #(nop)  VOLUME [var/www/html]        0B                  
2fb76a304e03        About an hour ago   /bin/sh -c #(nop)  EXPOSE 80                    0B                  
ec1a73b2e7d6        About an hour ago   /bin/sh -c yum install -y httpd                 52.8MB              
031f7a8b74a0        About an hour ago   /bin/sh -c rpmdb --rebuilddb                    6.64MB              
c32fc667b5f3        About an hour ago   /bin/sh -c #(nop) COPY file:254d80ba480dfa06…   71B                 
0a3eb3fde7fd        4 years ago                                                         140MB               Imported from -

测试页面是否可以正常访问


[root@foundation19 docker]# mkdir webdata
[root@foundation19 docker]# mv index.html webdata/
[root@foundation19 docker]# ls
Dockerfile  webdata  yum.repo

[root@foundation19 docker]# docker rm -f vm1 
vm1
[root@foundation19 docker]# docker run -d --name vm1 -v /tmp/docker/webdata:/var/www/html rhel7:v2
a8203a3b35eeeec170b7283fbbda136cffebc180a41c49891d3dd80c99f0e8ed
[root@foundation19 docker]# curl 172.17.0.2     ##可以访问代表正常
www.westos.org

直接在数据卷中编写发布文件


[root@foundation19 docker]# docker rm -f vm1
vm1
[root@foundation19 docker]# docker run -d --name vm1 rhel7:v2

查看vm1的数据卷位置


[root@foundation19 docker]# docker inspect vm1

在这里插入图片描述

进入数据卷位置并编写发布文件并测试

[root@foundation19 docker]# cd /var/lib/docker/volumes/f03725ca02f048a96dc78ed02f3c9b1c29b198458d99a0765e7d51d56d22def9/_data
[root@foundation19 _data]# cp /tmp/docker/webdata/index.html .
[root@foundation19 _data]# ls
index.html
[root@foundation19 _data]# curl 172.17.0.2
www.westos.org

[root@foundation19 _data]# echo hello,world >> index.html 
[root@foundation19 _data]# cat index.html 
www.westos.org
hello,world
[root@foundation19 _data]# curl 172.17.0.2
www.westos.org
hello,world

只读挂载

[root@foundation19 docker]# docker rm -f vm1
vm1
[root@foundation19 ~]# docker run -d --name vm1 -v /tmp/docker/webdata:/data:ro rhel7:v2

[root@foundation19 ~]# docker inspect vm1    ##找到source对应的数据卷位置
/var/lib/docker/volumes/267d70d0fec9229a426c4e14f83b614ae4bc5acdbc2723862e0af006a78a2ec9/_data

##删除之前的数据卷
[root@foundation19 ~]# docker volume rm f03725ca02f048a96dc78ed02f3c9b1c29b198458d99a0765e7d51d56d22def9

[root@foundation19 ~]# docker exec -it vm1 bash
bash-4.2# cd data/
bash-4.2# ls
index.html
bash-4.2# rm -fr index.html 
rm: cannot remove 'index.html': Read-only file system       ##删除文件被拒，显示只读Read-only
bash-4.2# cat index.html      ##可以正常读取
www.westos.org

二、Dockerfile的优化

以搭建nginx镜像为例演示如何加速Dockerfile

#需要有nginx的安装包
[root@foundation19 docker]# ls
Dockerfile   nginx-1.15.8.tar.gz  test  webdata  yum.repo
#编写Dockerfile
[root@foundation19 docker]# cat Dockerfile 
FROM rhel7
COPY yum.repo /etc/yum.repos.d/yum.repo
RUN rpmdb --rebuilddb && yum install -y gcc pcre-devel zlib-devel make
ADD nginx-1.15.8.tar.gz /mnt   ##ADD比COPY更强大，如果文件是可识别的压缩文件，会帮忙解压
WORKDIR /mnt/nginx-1.15.8
RUN sed -i 's/CFLAGS="$CFLAGS -g"/#CFLAGS="$CFLAGS -g"/g' auto/cc/gcc     ##关闭debug日志
RUN ./configure --prefix=/usr/local/nginx
RUN make
RUN make install
EXPOSE 80
VOLUME ["/usr/local/nginx/html"]
CMD ["/usr/local/nginx/sbin/nginx","-g","daemon off;"]

#封装镜像
[root@foundation19 docker]# docker build -t rhel7:v3 .

#创建容器
[root@foundation19 docker]# docker rm -f vm1
vm1
[root@foundation19 docker]# docker run -d --name nginx rhel7:v3

#测试nginx是否可以正常访问
[root@foundation19 docker]# docker inspect nginx
/var/lib/docker/volumes/2e9222ac2ddb8c79ea4391a9c4e6105dad6065cfcf2aa0f25c29273b9036769c/_data

[root@foundation19 docker]# cd /var/lib/docker/volumes/2e9222ac2ddb8c79ea4391a9c4e6105dad6065cfcf2aa0f25c29273b9036769c/_data
[root@foundation19 _data]# ls
50x.html  index.html
[root@foundation19 _data]# echo "hello,world" > index.html 
[root@foundation19 _data]# cat index.html 
hello,world
[root@foundation19 _data]# curl 172.17.0.2    #可以正常访问
hello,world

优化前，镜像大小为276MB
第一次优化

##将不想看到的输出都导入到垃圾箱
[root@foundation19 docker]# cat Dockerfile 
FROM rhel7
COPY yum.repo /etc/yum.repos.d/yum.repo
RUN rpmdb --rebuilddb && yum install -y gcc pcre-devel zlib-devel make  &> /dev/null && yum clean all
ADD nginx-1.15.8.tar.gz /mnt
WORKDIR /mnt/nginx-1.15.8
RUN sed -i 's/CFLAGS="$CFLAGS -g"/#CFLAGS="$CFLAGS -g"/g' auto/cc/gcc
RUN ./configure --prefix=/usr/local/nginx &> /dev/null
RUN make &> /dev/null
RUN make install &> /dev/null
RUN rm -fr /mnt/nginx-1.15.8
EXPOSE 80
VOLUME ["/usr/local/nginx/html"]
CMD ["/usr/local/nginx/sbin/nginx","-g","daemon off;"]

#重新封装一个镜像
[root@foundation19 docker]# docker build -t rhel7:v4 .
Successfully built fba2f9ad94cd
Successfully tagged rhel7:v4

可以看到镜像大小变小了
第二次优化

#将RUN都放在一行，减少层数
[root@foundation19 docker]# cat Dockerfile 
FROM rhel7
COPY yum.repo /etc/yum.repos.d/yum.repo
ADD nginx-1.15.8.tar.gz /mnt
WORKDIR /mnt/nginx-1.15.8
RUN rpmdb --rebuilddb && yum install -y gcc pcre-devel zlib-devel make  &> /dev/null && yum clean all && sed -i 's/CFLAGS="$CFLAGS -g"/#CFLAGS="$CFLAGS -g"/g' auto/cc/gcc && ./configure --prefix=/usr/local/nginx &> /dev/null && make &> /dev/null &&  make install &> /dev/null && rm -fr /mnt/nginx-1.15.8
EXPOSE 80
VOLUME ["/usr/local/nginx/html"]
CMD ["/usr/local/nginx/sbin/nginx","-g","daemon off;"]

[root@foundation19 docker]# docker build -t rhel7:v5 .

查看大小，有缩小2MB（效果不明显）
第三次优化

[root@foundation19 docker]# cat Dockerfile 
FROM rhel7 as build
COPY yum.repo /etc/yum.repos.d/yum.repo
ADD nginx-1.15.8.tar.gz /mnt
WORKDIR /mnt/nginx-1.15.8
RUN rpmdb --rebuilddb && yum install -y gcc pcre-devel zlib-devel make  &> /dev/null && yum clean all && sed -i 's/CFLAGS="$CFLAGS -g"/#CFLAGS="$CFLAGS -g"/g' auto/cc/gcc && ./configure --prefix=/usr/local/nginx &> /dev/null && make &> /dev/null &&  make install &> /dev/null && rm -fr /mnt/nginx-1.15.8

FROM rhel7
COPY --from=build /usr/local/nginx /usr/local/nginx
EXPOSE 80
CMD ["/usr/local/nginx/sbin/nginx","-g","daemon off;"]

 [root@foundation19 docker]# docker build -t rhel7:v6 .

现在封装出来的nginx只占1MB（141-140）
终极优化（从底层优化）

[root@foundation19 images]# docker load -i distroless.tar 
[root@foundation19 images]# docker load -i nginx.tar 

[root@foundation19 test]# vim Dockerfile 
[root@foundation19 test]# cat Dockerfile 
FROM nginx as base
# https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
ARG Asia/Shanghai

RUN mkdir -p /opt/var/cache/nginx && \
    cp -a --parents /usr/lib/nginx /opt && \
    cp -a --parents /usr/share/nginx /opt && \
    cp -a --parents /var/log/nginx /opt && \
    cp -aL --parents /var/run /opt && \
    cp -a --parents /etc/nginx /opt && \
    cp -a --parents /etc/passwd /opt && \
    cp -a --parents /etc/group /opt && \
    cp -a --parents /usr/sbin/nginx /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libpcre.so.* /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libz.so.* /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libc.so.* /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libdl.so.* /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libpthread.so.* /opt && \
    cp -a --parents /lib/x86_64-linux-gnu/libcrypt.so.* /opt && \
    cp -a --parents /usr/lib/x86_64-linux-gnu/libssl.so.* /opt && \
    cp -a --parents /usr/lib/x86_64-linux-gnu/libcrypto.so.* /opt && \
    cp /usr/share/zoneinfo/${TIME_ZONE:-ROC} /opt/etc/localtime

FROM gcr.io/distroless/base

COPY --from=base /opt /

EXPOSE 80

ENTRYPOINT ["nginx", "-g", "daemon off;"]

[root@foundation19 test]# docker build -t rhel7:v7 .

现在整个镜像只有 23.2MB
测试一下这么小的镜像能否正常使用

[root@foundation19 test]# docker run -d --name nginx rhel7:v7

输入http://172.17.0.2/ ，访问成功！在这里插入图片描述

三、 Dockerfile文件中CMD和ENTRYPOINT的区别

ENTRYPOINT 容器启动后执行的命令,让容器执行表现的像一个可执行程序一样,与CMD 的区别是不可以被 docker run 覆盖 , 会把 docker run 后面的参数当作传递给ENTRYPOINT 指令的参数。Dockerfile 中只能指定一个 ENTRYPOINT,如果指定了很多,只有最后一个有效。 docker run 命令的 -entrypoint 参数可以把指定的参数继续传递给ENTRYPOINT

测试1

[root@foundation19 images]# docker load -i busybox.tar 
[root@foundation19 ~]# cd /tmp/docker/
[root@foundation19 docker]# mkdir test
[root@foundation19 docker]# cd test/
[root@foundation19 test]# pwd
/tmp/docker/test
[root@foundation19 test]# vim Dockerfile
FROM busybox
ENV name world
CMD echo "hello,$name"

[root@foundation19 test]# docker build -t busybox:v1 .
[root@foundation19 test]# docker run --rm busybox:v1
hello,world

测试2

[root@foundation19 test]# cat Dockerfile 
FROM busybox
ENV name world
CMD ["/bin/echo","hello,$name"]
[root@foundation19 test]# docker build -t busybox:v2 .
[root@foundation19 test]# docker run --rm busybox:v2
hello,$name

测试3

[root@foundation19 test]# cat Dockerfile 
FROM busybox
ENV name world
CMD ["/bin/sh","-c","echo hello, $name"]

[root@foundation19 test]# docker build -t busybox:v3 .
[root@foundation19 test]# docker run --rm busybox:v3
hello, world

测试4

[root@foundation19 test]# cat Dockerfile 
FROM busybox
ENTRYPOINT ["/bin/echo", "hello"]
CMD ["world"]
[root@foundation19 test]# docker build -t busybox:v4 .

[root@foundation19 test]# docker run --rm busybox:v4
hello world
[root@foundation19 test]# docker run --rm busybox:v4 westos
hello westos