Docker容器怎么访问宿主机的服务

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If I have already launched mysql database service in the host server, and now I want allow the service in a docker container instance to access the host’s mysql service. What should I do?

如果宿主机上已经部署了mysql服务, 怎样才能让docker 得容器实例中的程序访问到mysql服务呢？

I found answer from the stackoverflow:

通过搜索，我找到了以下相关线索：

For example, on my system:

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>$ ip addr show docker0
>7: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
>link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
>inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
>valid_lft forever preferred_lft forever
>inet6 fe80::f4d2:49ff:fedd:28a0/64 scope link 
>valid_lft forever preferred_lft forever
>

And inside a container:

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>$ ip route show
>default via 172.17.0.1 dev eth0 
>172.17.0.0/16 dev eth0  src 172.17.0.4 
>

It’s fairly easy to extract this IP address using a simple shell script:

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>#!/bin/sh
>hostip=$(ip route show | awk '/default/ {print $3}')
>echo $hostip
>

You may need to modify the iptables rules on your host to permit connections from Docker containers. Something like this will do the trick:

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>$ iptables -A INPUT -i docker0 -j ACCEPT
>

This would permit access to any ports on the host from Docker containers. Note that:

  • iptables rules are ordered, and this rule may or may not do the right thing depending on what other rules come before it.
  • you will only be able to access host services that are either (a) listening on INADDR_ANY (aka 0.0.0.0) or that are explicitly listening on the docker0 interface.

REF：https://stackoverflow.com/questions/31324981/how-to-access-host-port-from-docker-container/31328031