Docker Machine — moby: Name or service not known

I have been running Docker on OS X for quite a while now and the I switched to Docker Machine for Mac Beta few months back. It has been a great experience so far, but not without occasional hiccups. I run some of my containers in host networking mode, and I have faced the following problem when I start some of my containers.

java.net.UnknownHostException: moby: moby: Name or service not known
at java.net.InetAddress.getLocalHost(InetAddress.java:1505) ~[na:1.8.0_102]
at com.netflix.eureka.transport.JerseyReplicationClient.createReplicationClient(JerseyReplicationClient.java:170) ~[eureka-core-1.4.9.jar!/:1.4.9]
at com.netflix.eureka.cluster.PeerEurekaNodes.createPeerEurekaNode(PeerEurekaNodes.java:194) [eureka-core-1.4.9.jar!/:1.4.9]
....
Caused by: java.net.UnknownHostException: moby: Name or service not known
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[na:1.8.0_102]
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928) ~[na:1.8.0_102]
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323) ~[na:1.8.0_102]
at java.net.InetAddress.getLocalHost(InetAddress.java:1500) ~[na:1.8.0_102]
... 67 common frames omitted

‘Moby’ is the name given to the host system that runs behind the scenes with Docker Machine for Mac (and Windows). Docker Machine for Mac runs MobyLinux VM, and the hostname file refers to itself as ‘moby’. But this entry is missing in the /etc/hosts file and my services fail to start up because it cannot resolve ‘moby’ to an IP. The workaround is simple. Just add the ‘add-host’ flag to your Docker run command telling it that ‘moby’ is ‘127.0.0.1’, like so:

docker run --net=host --add-host=moby:127.0.0.1 yourid/yourimage

This will automatically add an entry to the /etc/hosts file saying that moby in fact is 127.0.0.1.

Happy Dockerizing!