app-admin/kubelet-wrapper: Specify hosts-entry to mount hosts file

[weikinhuang]

This fixes an issue with the v1.8.x hyperkube images switching to debian base and missing an internal hosts file. Which causes lookups to localhost to fail.

Refs issue: kubernetes-retired/bootkube#740

[weikinhuang]

Quoting @euank from mentioned issue:

I suspect the root cause of that hosts file difference is this kubernetes change: kubernetes/kubernetes#48535

Rather than bindmounting through /etc/hosts, the rkt option --hosts-entry=host should copy over the hosts entry you have in /etc/hosts.

We'd be happy to take a PR against the kubelet-wrapper in the coreos-overlay repo if you'd like to (do note you'll need to bump the ebuild revision too if you do make such a PR).

Other fixes could be for the upstream hyperkube image to continue including a proper /etc/hosts file, or for the kubelet to only use 127.0.0.1 instead of relying on localhost to resolve to it.

I might make that last change when I get time.

I do think that this is not a bootkube issue but rather a kubernetes+hyperkube or container-linux+kubelet-wrapper issue.

[euank]

0.0.2-r1 -> 0.0.3 would be a more typical version bump.

Once that rename is done, LGTM

[weikinhuang]

done

[dghubble]

Works for me to address port-forward being broken when running on GCE.

There are more details in the issue @weikinhuang linked, but whether port-forward works depends on whether kubelet localhost can be resolved, which varies depending on the network / platform. Some of them mask this issue. Fix LGTM

[weikinhuang]

thanks!

[euank]

Thank you.

This should end up in the next set of releases; in the meanwhile overriding the option in the unit will be easier, but at least it can just be a temporary hack.

[dghubble]

Yeah, there are several places we can patch this in the mean time. On it.