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DockerFile的指令
FROM 基础镜像，一切从这里开始构建
MAINTAINER 镜像是谁写的 姓名+邮箱
RUN 镜像构建的时候需要运行的命令
ADD 步骤：tomcat镜像，这个tomcat压缩包！添加内容
WORKDIR 镜像的工作目录
VOLUME 挂载的目录
EXPOST 保留端口配置\
CMD 指定这个容器启动的时候要运行的命令，只有最后一个会生效，可被代替
ENTRYPOINT 指定这个容器启动的时候要运行的命令，可以追加命令
ONBUILD 当构建一个被继承Dockerfile，这个时候就会运行ONBUILD的指令，触发指令
COPY 类似ADD，将我们文件拷贝到镜像中
ENV 构建的时候设置环境变量\
CMD和ENTRYPOINT的区别
CMD 指定这个容器启动的时候要运行的命令，只有最后一个会生效，会被代替
ENTRYPOINT 指定这个容器启动的时候要运行的命令，可以追加命令
测试CMD
编写dockerfile文件
[root@VM-0-12-centos home]# ls
ceshi dockerfile docker-test-volume mysql www
[root@VM-0-12-centos home]# cd dockerfile
[root@VM-0-12-centos dockerfile]# ls
[root@VM-0-12-centos dockerfile]# vim dockerfile-cmd-test
[root@VM-0-12-centos dockerfile]# cat dockerfile-cmd-test
FROM centos
CMD ["ls","-a"]
构建镜像
[root@VM-0-12-centos dockerfile]# docker build -f dockerfile-cmd-test
"docker build" requires exactly 1 argument.
See 'docker build --help'.
Usage: docker build [OPTIONS] PATH | URL | -
Build an image from a Dockerfile
[root@VM-0-12-centos dockerfile]# docker build -f dockerfile-cmd-test -t cmdtest .
Sending build context to Docker daemon 2.048kB
Step 1/2 : FROM centos
---> 5d0da3dc9764
Step 2/2 : CMD ["ls","-a"]
---> Running in 419baf5895ff
Removing intermediate container 419baf5895ff
---> 1539fed5670d
Successfully built 1539fed5670d
Successfully tagged cmdtest:latest
run运行
[root@VM-0-12-centos dockerfile]# docker run 1539fed5670d
.
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
想追加一个命令 -l ls -al 出现报错
[root@VM-0-12-centos dockerfile]# docker run 1539fed5670d -l
docker: Error response from daemon: OCI runtime create failed: container_linux.go:380: starting container process caused: exec: "-l": executable file not found in $PATH: unknown.
在cmd清理下 -l 替换了CMD ["ls","-a"] 命令，-l 不是命令所以报错！
测试ENTRYPOINT
[root@VM-0-12-centos dockerfile]# cat dockerfile-cmd-entrypoint
FROM centos
ENTRYPOINT ["ls","-a"]
[root@VM-0-12-centos dockerfile]# vim dockerfile-cmd-entrypoint
[root@VM-0-12-centos dockerfile]# docker build -f dockerfile-cmd-entrypoint -t entrypoint-test .
Sending build context to Docker daemon 15.87kB
Step 1/2 : FROM centos
---> 5d0da3dc9764
Step 2/2 : ENTRYPOINT ["ls","-a"]
---> Running in 897e33c72832
Removing intermediate container 897e33c72832
---> 91eaa82e9928
Successfully built 91eaa82e9928
Successfully tagged entrypoint-test:latest
[root@VM-0-12-centos dockerfile]# docker run ^C
[root@VM-0-12-centos dockerfile]# docker run 91eaa82e9928
.
..
.dockerenv
bin
dev
etc
home
lib
lib64
lost+found
media
mnt
opt
proc
root
run
sbin
srv
sys
tmp
usr
var
[root@VM-0-12-centos dockerfile]# docker run 91eaa82e9928 -l
total 56
drwxr-xr-x 1 root root 4096 Dec 17 03:20 .
drwxr-xr-x 1 root root 4096 Dec 17 03:20 ..
-rwxr-xr-x 1 root root 0 Dec 17 03:20 .dockerenv
lrwxrwxrwx 1 root root 7 Nov 3 2020 bin -> usr/bin
drwxr-xr-x 5 root root 340 Dec 17 03:20 dev
drwxr-xr-x 1 root root 4096 Dec 17 03:20 etc
drwxr-xr-x 2 root root 4096 Nov 3 2020 home
lrwxrwxrwx 1 root root 7 Nov 3 2020 lib -> usr/lib
lrwxrwxrwx 1 root root 9 Nov 3 2020 lib64 -> usr/lib64
drwx------ 2 root root 4096 Sep 15 14:17 lost+found
drwxr-xr-x 2 root root 4096 Nov 3 2020 media
drwxr-xr-x 2 root root 4096 Nov 3 2020 mnt
drwxr-xr-x 2 root root 4096 Nov 3 2020 opt
dr-xr-xr-x 158 root root 0 Dec 17 03:20 proc
dr-xr-x--- 2 root root 4096 Sep 15 14:17 root
drwxr-xr-x 11 root root 4096 Sep 15 14:17 run
lrwxrwxrwx 1 root root 8 Nov 3 2020 sbin -> usr/sbin
drwxr-xr-x 2 root root 4096 Nov 3 2020 srv
dr-xr-xr-x 13 root root 0 Dec 11 02:48 sys
drwxrwxrwt 7 root root 4096 Sep 15 14:17 tmp
drwxr-xr-x 12 root root 4096 Sep 15 14:17 usr
drwxr-xr-x 20 root root 4096 Sep 15 14:17 var
Dockerfile中很多命令都是十分的相似，
