Dockerfile

docker分层

用来构建docker镜像的文件

 

常用命令

 

CMD                     指定容器启动的时候运行的命令，只有最后一个会生效，可被替代
ENTRYPOINT        指定容器启动的时候运行的命令，可以追加命令
ONBUILD               当构建一个被继承Dockerfile，这时候会运行ONBUILD指令，触发指令
COPY                    将文件拷贝到镜像中，类似ADD
ENV                       设置环境变量

实战测试

DockerHub中大多数镜像都是从这个基础镜像来的，FROM scratch，然后配置需要的软件和配置

 

示例构建一个centos

FROM centos
 
 
MAINTAINER wzj<wusir666666@163.com>
 
 
ENV MYPATH /usr/local
 
 
WORKDIR $MYPATH
 
 
RUN yum -y install vim
 
 
RUN yum -y install net-tools
 
 
EXPOSE 80
 
 
CMD echo $MYPATH
 
 
CMD echo "---end---"
 
 
CMD /bin/bash

列出镜像变更历史（构建步骤）：docker history 镜像id

 ENTRYPOINT 和 CMD区别

CMD                指定容器启动的时候运行的命令，只有最后一个会生效，可被替代
ENTRYPOINT        指定容器启动的时候运行的命令，可以追加命令

测试CMD

构建镜像：
FROM centos
CMD ["ls", "-a"]
 
运行后显示
E:\study\docker\dockerfile>docker run centos_test:v1
.
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
 
如果此时想要追加一个命令 -l 
E:\study\docker\dockerfile>docker run centos_test:v1 -l
docker: Error response from daemon: OCI runtime create failed: container_linux.go:349: starting container process caused "exec: \"-l\": executable file not found in $PATH": unknown.
 
CMD情况下 -l 替换了 ["ls", "-a"]，但是-l不是一个有效命令，所以报错

测试ENTRYPOINT

构建镜像：
FROM centos
ENTRYPOINT ["ls", "-a"]
 
 
运行后显示
E:\study\docker\dockerfile>docker run centos_test:v1
.
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
 
 
如果此时想要追加一个命令 -l 
E:\study\docker\dockerfile>docker run centos_test1:v1  -l
total 56
drwxr-xr-x   1 root root 4096 Nov 25 09:23 .
drwxr-xr-x   1 root root 4096 Nov 25 09:23 ..
-rwxr-xr-x   1 root root    0 Nov 25 09:23 .dockerenv
lrwxrwxrwx   1 root root    7 May 11  2019 bin -> usr/bin
drwxr-xr-x   5 root root  340 Nov 25 09:23 dev
drwxr-xr-x   1 root root 4096 Nov 25 09:23 etc
drwxr-xr-x   2 root root 4096 May 11  2019 home
lrwxrwxrwx   1 root root    7 May 11  2019 lib -> usr/lib
lrwxrwxrwx   1 root root    9 May 11  2019 lib64 -> usr/lib64
drwx------   2 root root 4096 Aug  9 21:40 lost+found
drwxr-xr-x   2 root root 4096 May 11  2019 media
drwxr-xr-x   2 root root 4096 May 11  2019 mnt
drwxr-xr-x   2 root root 4096 May 11  2019 opt
dr-xr-xr-x 124 root root    0 Nov 25 09:23 proc
dr-xr-x---   2 root root 4096 Aug  9 21:40 root
drwxr-xr-x  11 root root 4096 Aug  9 21:40 run
lrwxrwxrwx   1 root root    8 May 11  2019 sbin -> usr/sbin
drwxr-xr-x   2 root root 4096 May 11  2019 srv
dr-xr-xr-x  13 root root    0 Nov 25 09:23 sys
drwxrwxrwt   7 root root 4096 Aug  9 21:40 tmp
drwxr-xr-x  12 root root 4096 Aug  9 21:40 usr
drwxr-xr-x  20 root root 4096 Aug  9 21:40 var