Query docker embedded dns from host
You can use socat
to expose the Docker network's resolver at 127.0.0.11:53
like cirocosta/expose-edns
image does, which is essentially:
socat UDP4-RECVFROM:53,fork,bind="0.0.0.0" UDP4-SENDTO:127.0.0.11:53
Then use it like:
host container_name_to_resolve `docker inspect --format \
'{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' socat_container_name`
Also note that the socat
container must be in the same Docker network as target containers.
Update
To overcome the limitation of the same Docker network, phensley/docker-dns
can be used (which uses Docker API). On an OS with NetworkManager and Dnsmasq enabled (otherwise can be enabled like described in this answer) you can run:
docker run -d --name docker-dns -v /var/run/docker.sock:/docker.sock \
phensley/docker-dns --domain docker --no-recursion
Then inspect its IP address with:
docker inspect --format \
'{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' docker-dns
And put it into /etc/NetworkManager/dnsmasq.d/docker.conf
like:
server=/docker/1.2.3.4
After systemctl restart NetworkManager
you should be able to address your Docker containers from host like ping CONTAINER_NAME.docker
which is quite handy for dockerised development environments.
Another way would be to use docker-dns. It's a docker container that exposes a dns server that resolves the docker containers.
Running it is as simple as
docker run -d --name dns -v /var/run/docker.sock:/docker.sock phensley/docker-dns
Consul
I like using Hashicorp's Consul for this. It can run as an installed client or container, and provides a DNS Interface that you can query external of Docker. It also has features like service discovery & monitoring, and is open source.
https://www.consul.io/docs/agent/dns.html
One of the primary query interfaces for Consul is DNS. The DNS interface allows applications to make use of service discovery without any high-touch integration with Consul.
For example, instead of making HTTP API requests to Consul, a host can use the DNS server directly via name lookups like "redis.service.east-aws.consul". This query automatically translates to a lookup of nodes that provide the redis service, are located in the "east-aws" datacenter, and have no failing health checks. It's that simple!
It might be overkill for what you're looking for, but should do the job.
DNSMasq
A simpler alternative might be DNSMasq. I'm not as familiar with it, but for a really small scale setting it would allow your host to be DNS aware of running containers.
http://www.thekelleys.org.uk/dnsmasq/doc.html
https://hub.docker.com/r/andyshinn/dnsmasq/