Docker 1.10 access a container by its hostname from a host machine

Question

I have the Docker version 1.10 with embedded DNS service.

I have created two service containers in my docker-compose file. They are reachable each other by hostname and by IP, but when I would like reach one of them from the host machine, it doesn't work, it works only with IP but not with hostname.

So, is it possible to access a docker container from the host machine by it's hostname in the Docker 1.10, please?

Update:

docker-compose.yml

version: '2' services:     service_a:         image: nginx         container_name: docker_a         ports:            - 8080:80     service_b:         image: nginx         container_name: docker_b         ports:             - 8081:80 

then I start it by command: docker-compose up --force-recreate

when I run:

• docker exec -i -t docker_a ping -c4 docker_b - it works
• docker exec -i -t docker_b ping -c4 docker_a - it works
• ping 172.19.0.2 - it works (172.19.0.2 is docker_b's ip)
• ping docker_a - fails

The result of the docker network inspect test_default is

[     {         "Name": "test_default",         "Id":   "f6436ef4a2cd4c09ffdee82b0d0b47f96dd5aee3e1bde068376dd26f81e79712",         "Scope": "local",         "Driver": "bridge",         "IPAM": {             "Driver": "default",             "Options": null,             "Config": [                 {                     "Subnet": "172.19.0.0/16",                     "Gateway": "172.19.0.1/16"                 }             ]         },         "Containers": {              "a9f13f023761123115fcb2b454d3fd21666b8e1e0637f134026c44a7a84f1b0b": {                 "Name": "docker_a",                 "EndpointID":     "a5c8e08feda96d0de8f7c6203f2707dd3f9f6c3a64666126055b16a3908fafed",                 "MacAddress": "02:42:ac:13:00:03",                 "IPv4Address": "172.19.0.3/16",                 "IPv6Address": ""             },                 "c6532af99f691659b452c1cbf1693731a75cdfab9ea50428d9c99dd09c3e9a40": {                 "Name": "docker_b",                 "EndpointID":     "28a1877a0fdbaeb8d33a290e5a5768edc737d069d23ef9bbcc1d64cfe5fbe312",                 "MacAddress": "02:42:ac:13:00:02",                 "IPv4Address": "172.19.0.2/16",                 "IPv6Address": ""             }         },         "Options": {}     } ] 

Answer 1

As answered here there is a software solution for this, copying the answer:

---

There is an open source application that solves this issue, it's called DNS Proxy Server

It's a DNS server that resolves container hostnames, and when it can't resolve a hostname then it can resolve it using public nameservers.

Start the DNS Server

$ docker run --hostname dns.mageddo --name dns-proxy-server -p 5380:5380 \ -v /var/run/docker.sock:/var/run/docker.sock \ -v /etc/resolv.conf:/etc/resolv.conf \ defreitas/dns-proxy-server 

It will set as your default DNS automatically (and revert back to the original when it stops).

Start your container for the test

docker-compose up 

docker-compose.yml

version: '2' services:   redis:     container_name: redis     image: redis:2.8     hostname: redis.dev.intranet     network_mode: bridge # that way he can solve others containers names even inside, solve elasticsearch, for example   elasticsearch:     container_name: elasticsearch     image: elasticsearch:2.2     hostname: elasticsearch.dev.intranet 

Now resolve your containers' hostnames

from host

$ nslookup redis.dev.intranet Server:     172.17.0.2 Address:    172.17.0.2#53  Non-authoritative answer: Name:   redis.dev.intranet Address: 172.21.0.3 

from another container

$ docker exec -it redis ping elasticsearch.dev.intranet PING elasticsearch.dev.intranet (172.21.0.2): 56 data bytes 

As well it resolves Internet hostnames

$ nslookup google.com Server:     172.17.0.2 Address:    172.17.0.2#53  Non-authoritative answer: Name:   google.com Address: 216.58.202.78 

Answer 2

Here's what I do.

I wrote a Python script called dnsthing, which listens to the Docker events API for containers starting or stopping. It maintains a hosts-style file with the names and addresses of containers. Containers are named <container_name>.<network>.docker, so for example if I run this:

docker run --rm --name mysql -e MYSQL_ROOT_PASSWORD=secret  mysql 

I get this:

172.17.0.2 mysql.bridge.docker 

I then run a dnsmasq process pointing at this hosts file. Specifically, I run a dnsmasq instance using the following configuration:

listen-address=172.31.255.253 bind-interfaces addn-hosts=/run/dnsmasq/docker.hosts local=/docker/ no-hosts no-resolv 

And I run the dnsthing script like this:

dnsthing -c "systemctl restart dnsmasq_docker" \   -H /run/dnsmasq/docker.hosts --verbose 

So:

• dnsthing updates /run/dnsmasq/docker.hosts as containers stop/start
• After an update, dnsthing runs systemctl restart dnsmasq_docker
• dnsmasq_docker runs dnsmasq using the above configuration, bound to a local bridge interface with the address 172.31.255.253.

• The "main" dnsmasq process on my system, maintained by NetworkManager, uses this configuration from /etc/NetworkManager/dnsmasq.d/dockerdns:

  server=/docker/172.31.255.253 

  That tells dnsmasq to pass all requests for hosts in the .docker domain to the docker_dnsmasq service.

This obviously requires a bit of setup to put everything together, but after that it seems to Just Work:

$ ping -c1  mysql.bridge.docker PING mysql.bridge.docker (172.17.0.2) 56(84) bytes of data. 64 bytes from 172.17.0.2: icmp_seq=1 ttl=64 time=0.087 ms  --- mysql.bridge.docker ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.087/0.087/0.087/0.000 ms