implement --dns flag to allow overriding nameservers

[chanwit]

This PR implements a new flag, --dns, to allow overriding DNS nameservers in the VM's /etc/resolv.conf.

Signed-off-by: Chanwit Kaewkasi [email protected]

[chanwit]

@stealthybox please review this one instead of #421 Thank you

[stealthybox]

I think the flag interface is a good start. Need a further review on the annotations -- maybe we should have a struct instead.

For the implementation, I'm not sure if DHCP solution is better than using the runtime's resolv.conf. It's certainly nice that since it's done through the vmDir/manifest, it does not need to be re-implemented in the runtime -- that's a really good thing.

We can remove the need for the dns flags for unrelated e2e tests in this patch and add specific ones that just test the resulting /etc/resolv.conf in the vm FS.

Removing this from the milestone for now.

[bbros-dev]

I think the flag interface is a good start.

Please could Ignite turn away from this path of adding API (cli flags) config data in this 'atomic' fashion? It leads to nightmares such as this example (from docker).

If the issue here is that a different resolv.conf file is needed, address that directly:

--resolv string              Specify a path to a resolv.conf to override the default file.

In fact copyFiles --copy-files should be sufficient here? Happy to elaborate if required.