Docker Name Resolution issues

  • Hi all,


    after a looooooong time I now upgraded to OMV 5.x and started with a fresh install, attached the old disks and got everyting running. Now I try to setup some of the more fancier plugins, but this time as containers (such as mariaDB for Kodi, nzbget and sickchill).


    I deployed the docker plugin and activated Portainer. I also then deployed mariaDB, imported my old KODI database and also got sickchill running and same for nzbget. I can download stuff, I can organize my TV shows and so on. Great.


    Now I have a problem getting sickchill connected to nzbget and other way around.


    Before I deployed a the two containers with Portainer, I created a new bridged network "media" where I put both containers in. I learned that I need this to enable host name resoltion for the containers.


    I also added the hostname for the containers inside the configuraition of Portainer.


    When I now try to ping from sickchill instance to nzbget everything works as expected:

    root@openmediavault:/Storage/appdata/nzbget/scripts# docker exec -ti sickchill ping nzbget

    PING nzbget (172.19.0.2): 56 data bytes

    64 bytes from 172.19.0.2: seq=0 ttl=64 time=0.158 ms

    64 bytes from 172.19.0.2: seq=1 ttl=64 time=0.193 ms

    64 bytes from 172.19.0.2: seq=2 ttl=64 time=0.187 ms

    64 bytes from 172.19.0.2: seq=3 ttl=64 time=0.186 ms


    Also connecting to the port works:

    root@openmediavault:/Storage/appdata/nzbget/scripts# docker exec -ti sickchill nc -zv nzbget 6789

    nzbget (172.19.0.2:6789) open


    However Sickrage allways complains about this error message:

    2021-01-22 14:29:16 WARNING :: SEARCHQUEUE-BACKLOG-95011 :: Please check your NZBget host and port (if it is running). NZBget is not responding to this combination


    The entry for sickrage is: nzbget:6789


    The only thing that does not work is nslookup of nzbget server. Even if ping and nc work.


    I then added /etc/hosts entries to the containers (via Portainer of cause) and that fixed it - it works. So at least now I have a workaround in place.


    However as the IP addresses assigned to the containers are simply random and not bound, so eventually the /etc/hosts entries will break some time in the future.


    I do NOT want to get host network using this and actually I am surprised why that does not work.


    Anyone has any idea on how to actually get this working properly? Anything I am missing?

    Everything is possible, sometimes it requires Google to find out how.

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