Search code examples
dockerdocker-swarm

cant ping docker container by name from host

I have many containers on my server, I need to access all containers by the name(not IP). and of course, I can ping containers by IP address. problem is I can't ping them by hostname or name.

also, I don't using docker-compose. I use docker file and docker restapi

Solution

  • Option A: run a DNS proxy server container

    Here is a DNS proxy server project that can do this: https://github.com/mageddo/dns-proxy-server

    First, you need to start the DNS proxy server:

    docker run --rm --hostname dns.mageddo -v /var/run/docker.sock:/var/run/docker.sock -v /etc/resolv.conf:/etc/resolv.conf defreitas/dns-proxy-server

    Then, run a dummy container and assign it a --hostname for testing purpose:

    docker run -d --hostname=this-can-be-resolved-from-host nginx

    Finally, try to resolve/ping/curl the name you assigned to the nginx container in the previous step, from your host machine:

    neo@neo-desktop:~$ nslookup this-can-be-resolved-from-host
Server:     172.17.0.4
Address:    172.17.0.4#53

Non-authoritative answer:
Name:   this-can-be-resolved-from-host
Address: 172.17.0.3
Name:   this-can-be-resolved-from-host
Address: 172.17.0.3


    neo@neo-desktop:~$ ping this-can-be-resolved-from-host
PING this-can-be-resolved-from-host (172.17.0.3) 56(84) bytes of data.
64 bytes from 172.17.0.3 (172.17.0.3): icmp_seq=1 ttl=64 time=0.032 ms

    neo@neo-desktop:~$ curl this-can-be-resolved-from-host
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
[...]


    Option B: Run an injector that adds the container names directly in the hosts file, on the docker host:
    (solution found by the OP @Tokyo Developer)

    Here is a simple "etc/hosts" file injection tool: https://github.com/dvddarias/docker-hoster

    Run the injector container:

    docker run -d \
    -v /var/run/docker.sock:/tmp/docker.sock \
    -v /etc/hosts:/tmp/hosts \
    dvdarias/docker-hoster

    Run a dummy container and assign it a --hostname for testing purpose:

    docker run -d --hostname=this-can-be-resolved-from-host nginx

    Try to resolve the hostname AND the container name assigned to the nginx container in the previous step, from your host machine:

    nslookup this-can-be-resolved-from-host
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   this-can-be-resolved-from-host
Address: 172.17.0.3

    nslookup keen_lamarr
Server:     127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
Name:   keen_lamarr
Address: 172.17.0.3