Dockerfile的EXPOSE-编程知识

文章目录

环境
总结
测试
- 使用EXPOSE
- - 测试1：不做端口映射
  - 测试2：-p 8080:80
  - 测试3：-P
  - 测试4：--network=host
- 不使用EXPOSE
参考

环境

RHEL 9.3
Docker Community 24.0.7

总结

如果懒得看测试的详细信息，可以直接看结果：

`docker run` 选项	在Dockerfile里 `EXPOSE 80`	在Dockerfile里不 `EXPOSE 80`	备注
无	在容器外无法访问容器的80端口	在容器外无法访问容器的80端口
`-p 8080:80`	8080	8080	显式指定映射端口
`-P`	随机端口	随机端口	随机映射端口
`--network=host`	80	80	直接使用容器的端口

所以，EXPOSE并不会真正开放端口，它更像是一个说明文档，由image的开发者声明image所监听的端口，使用者以此为依据，在启动容器时，可以以不同的策略来开放端口。

测试

使用EXPOSE

创建 Dockerfile 文件如下：

FROM nginx:alpineEXPOSE 80

构建：

docker build -t kai0107_1 .

测试1：不做端口映射

启动容器：

docker run kai0107_1

查看容器：

➜  ~ docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS     NAMES
430b0c2bee65   kai0107_1   "/docker-entrypoint.…"   5 seconds ago   Up 5 seconds   80/tcp    recursing_noyce

检查该容器：

➜  ~ docker container inspect 430b0c2bee65 | grep -i3 port"Config": {}},"NetworkMode": "default","PortBindings": {},"RestartPolicy": {"Name": "no","MaximumRetryCount": 0
--"OomScoreAdj": 0,"PidMode": "","Privileged": false,"PublishAllPorts": false,"ReadonlyRootfs": false,"SecurityOpt": null,"UTSMode": "",
--"AttachStdin": false,"AttachStdout": true,"AttachStderr": true,"ExposedPorts": {"80/tcp": {}},"Tty": false,
--"HairpinMode": false,"LinkLocalIPv6Address": "","LinkLocalIPv6PrefixLen": 0,"Ports": {"80/tcp": null},"SandboxKey": "/var/run/docker/netns/c762f4dc271b",

注：可以用 -f 选项指定输出格式，参见 https://docs.docker.com/engine/reference/commandline/inspect 。

打开浏览器，访问 http://localhost:80 ，如下：

在这里插入图片描述

可见，在容器之外，无法访问80端口。

测试2：-p 8080:80

启动容器：

docker run -p 8080:80 kai0107_1

查看容器：

➜  ~ docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED              STATUS              PORTS                                   NAMES
dd9ea9e98b4b   kai0107_1   "/docker-entrypoint.…"   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp, :::8080->80/tcp   naughty_almeida

注： 0.0.0.0 和 :: 都是代表匹配所有IP地址。前者是IPv4的写法，后者是IPv6的写法。

检查该容器：

➜  ~ docker container inspect dd9ea9e98b4b | grep -i3 port"Config": {}},"NetworkMode": "default","PortBindings": {"80/tcp": [{"HostIp": "","HostPort": "8080"}]},
--"OomScoreAdj": 0,"PidMode": "","Privileged": false,"PublishAllPorts": false,"ReadonlyRootfs": false,"SecurityOpt": null,"UTSMode": "",
--"AttachStdin": false,"AttachStdout": true,"AttachStderr": true,"ExposedPorts": {"80/tcp": {}},"Tty": false,
--"HairpinMode": false,"LinkLocalIPv6Address": "","LinkLocalIPv6PrefixLen": 0,"Ports": {"80/tcp": [{"HostIp": "0.0.0.0","HostPort": "8080"},{"HostIp": "::","HostPort": "8080"}]},

打开浏览器，访问 http://localhost:8080 ，如下：

在这里插入图片描述

可见，在容器外部，可以通过8080端口访问容器里的80端口。

测试3：-P

启动容器：

docker run -P kai0107_1

查看容器：

➜  ~ docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                                     NAMES
241fd7f0ee87   kai0107_1   "/docker-entrypoint.…"   5 seconds ago   Up 4 seconds   0.0.0.0:32768->80/tcp, :::32768->80/tcp   jovial_haslett

检查该容器：

➜  ~ docker container inspect 241fd7f0ee87 | grep -i3 port"Config": {}},"NetworkMode": "default","PortBindings": {},"RestartPolicy": {"Name": "no","MaximumRetryCount": 0
--"OomScoreAdj": 0,"PidMode": "","Privileged": false,"PublishAllPorts": true,"ReadonlyRootfs": false,"SecurityOpt": null,"UTSMode": "",
--"AttachStdin": false,"AttachStdout": true,"AttachStderr": true,"ExposedPorts": {"80/tcp": {}},"Tty": false,
--"HairpinMode": false,"LinkLocalIPv6Address": "","LinkLocalIPv6PrefixLen": 0,"Ports": {"80/tcp": [{"HostIp": "0.0.0.0","HostPort": "32768"},{"HostIp": "::","HostPort": "32768"}]},

打开浏览器，访问 http://localhost:32768 ，如下：

在这里插入图片描述

可见，在容器外部，可以通过32768端口访问容器里的80端口。

注意：32768是一个随机端口。下次再启动容器时，可能就是另外一个端口了。

测试4：–network=host

启动容器：

docker run --network=host kai0107_1

查看容器：

➜  ~ docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS     NAMES
adcbcdd4698c   kai0107_1   "/docker-entrypoint.…"   6 seconds ago   Up 6 seconds             quizzical_hugle

检查该容器：

➜  ~ docker container inspect adcbcdd4698c | grep -i3 port"Config": {}},"NetworkMode": "host","PortBindings": {},"RestartPolicy": {"Name": "no","MaximumRetryCount": 0
--"OomScoreAdj": 0,"PidMode": "","Privileged": false,"PublishAllPorts": false,"ReadonlyRootfs": false,"SecurityOpt": null,"UTSMode": "",
--"AttachStdin": false,"AttachStdout": true,"AttachStderr": true,"ExposedPorts": {"80/tcp": {}},"Tty": false,
--"HairpinMode": false,"LinkLocalIPv6Address": "","LinkLocalIPv6PrefixLen": 0,"Ports": {},"SandboxKey": "/var/run/docker/netns/default","SecondaryIPAddresses": null,"SecondaryIPv6Addresses": null,