Docker内如何访问本机(宿主机)

红太狼 2022-05-23 03:38 408阅读 0赞

### Question ###

Docker内需要访问本机的数据库，如何访问。使用`127.0.0.1`肯定是不行的，因为这个在Docker容器里面指的是容器本身。所以，需要走别动渠道进行解决。

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### Solution ###

下面几种办法，根据操作系统的类型，选取其一即可。

*  DockerFile：

RUN /sbin/ip route|awk '/default/ { print  $3,"\tdockerhost" }' >> /etc/hosts

*  RunTime：

(may not use) docker run --add-host dockerhost:`/sbin/ip route|awk '/default/ { print  $3}'` [my container] (useful) docker run --add-host=dockerhost:`docker network inspect --format='{
       {range .IPAM.Config}}{
       {.Gateway}}{
       {end}}' bridge` [IMAGE]

*  Docker for Mac (17.12+):

docker.for.mac.host.internal
    MONGO_SERVER=docker.for.mac.host.internal
    
    # docker-compose.yml
    version: '3'
    
    services:
      api:
        build: ./api
        volumes:
          - ./api:/usr/src/app:ro
        ports:
          - "8000"
        environment:
          - MONGO_SERVER
        command: /usr/local/bin/gunicorn -c /usr/src/app/gunicorn_config.py -w 1 -b :8000 wsgi

*  Linux

＃ Solution 1
    /sbin/ip route|awk '/default/ { print $3 }'
    docker run --add-host dockerhost:`/sbin/ip route|awk '/default/ { print  $3}'` [my container] ＃ Solution 2 -e "DOCKER_HOST=$(ip -4 addr show docker0 | grep -Po 'inet \K[\d.]+')"

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### Principle ###

想知道原理，需要了解计算机网络的模型和docker实现的模型。docker内部实际上实现了一个虚拟网桥docker0，需要通过网桥找到外部宿主机的在网桥的虚拟地址，也就是`docker.for.mac.host.internal`，就可以实现容器内访问外部宿主机。感兴趣的话可以了解下Docker的网络原理、计算机网络原理和docker compose等内容。

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### Reference ###

\[1\]. [(stackoverflow)insert-docker-parent-host-ip-into-containers-hosts-file][stackoverflow_insert-docker-parent-host-ip-into-containers-hosts-file]

\[2\]. [(stackoverflow)how-to-get-the-ip-address-of-the-docker-host-from-inside-a-docker-container][stackoverflow_how-to-get-the-ip-address-of-the-docker-host-from-inside-a-docker-container]

[stackoverflow_insert-docker-parent-host-ip-into-containers-hosts-file]: https://stackoverflow.com/questions/26864180/insert-docker-parent-host-ip-into-containers-hosts-file/26864854#26864854
[stackoverflow_how-to-get-the-ip-address-of-the-docker-host-from-inside-a-docker-container]: https://stackoverflow.com/questions/22944631/how-to-get-the-ip-address-of-the-docker-host-from-inside-a-docker-container