kxuan / docker-name-resolver

docker container name resolver

Docker Name Resolver

Resolve docker container's name to its ip address on host machine.

In docker container, you can get the ip address of another container using its name or id. But the name or id can not be used on the host. Because docker's embedded DNS server only bind to its container's network namespace.

This program can resolve container's name or id to its ip address on host, so you can connect to container using its name.

Feature

• Resolve container's name or id to its IP address
• Support remote docker host

Install

1. Download from release or build main.go manual

   go build main.go

2. Start docker-name-resolver

   ./docker-name-resolver

3. Depends on your DNS resolver, you have to modify its config.

   • for systemd-resolved:
     1. Create docker-name-resolver.conf in /etc/systemd/resolved.conf.d, and write the following text:

        [Resolve]
        DNS=127.0.0.11
        Domains=~docker.
        

        You can change ~docker. to any suffix you like. For example, if you want to resolve <container-name>.container to <container-name>'s ip, you can use Domains=~container.
     2. restart systemd-resolved

        systemctl restart systemd-resolved

   • for dnsmasq
     1. Append this line to your dnsmasq config file. (Typically /etc/dnsmasq.conf)

        server=/docker/127.0.0.11
        

     2. restart dnsmasq

        systemctl restart dnsmasq

4. Test <container-name>.docker

$ docker run --name hello -d ubuntu /bin/sleep 100
987173b0d8f7fba5319e93cea25a2797dd14428516a5f008c527cf5bd59097f9
$ ping hello.docker
PING hello.docker (192.168.123.3) 56(84) bytes of data.
64 bytes from 192.168.123.3: icmp_seq=1 ttl=64 time=0.041 ms

Usage

Arguments are passing by environment

Variable	Description	Example
DOCKER_HOST	The docker host to query containers. (See -H option docker(1) manual) (Default: local)	tcp://192.168.1.2:2376
BIND_ADDRESS	Address to bind DNS server (Default: 127.0.0.11)	127.0.0.11

Example

• Resolve container on remote host

You can specify remote host by environment variable DOCKER_HOST

export DOCKER_HOST=tcp://192.168.1.2:
./docker-name-resolver

License

Apache