docker container gives unknowHost exception when
ping "private Network hostname" ping: unknown host
But when I ping by IP it gives result
8 packets transmitted, 8 packets received, 0% packet loss
The work around seems to be adding host entry to /etc/hosts file in the running docker container but I am using the docker in K8 platform that dynamically creates new container so I can not manually add host entries. I was wondering why it can not resolve host name. Any help appreciated :)
You can add hostAliases in Pod Spec. For details, see the official doc.
Here is an example of Pod where hostAliases are used:
apiVersion: v1
kind: Pod
metadata:
name: hostaliases-pod
spec:
restartPolicy: Never
hostAliases:
- ip: "8.8.8.8"
hostnames:
- "foo.local"
- "bar.local"
containers:
- name: cat-hosts
image: busybox
command:
- ping
args:
- "foo.local"If we see the logs of the pod:
$ kubectl logs po/hostaliases-pod
PING foo.local (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: seq=0 ttl=61 time=51.333 ms
64 bytes from 8.8.8.8: seq=1 ttl=61 time=59.600 ms
....As it is said in official doc, there is some limitations:
HostAlias is only supported in 1.7+.
HostAlias support in 1.7 is limited to non-hostNetwork Pods because kubelet only manages the hosts file for non-hostNetwork Pods.
In 1.8, HostAlias is supported for all Pods regardless of network configuration.