[Feature] add: config options to configure extra hosts

[iwilltry42]

Changelog

Legend:

• 💻 = exposed change, visible to end users, e.g. CLI flags and config options
• 🧰 = internal change, usually invisible for end users, but important for developers

Added

• 💻 new CLI flag k3d cluster create --host-alias <ip>:<hostname>[,alias,...] (can be used multiple times)
  • will add /etc/hosts style entries to /etc/hosts in the node containers and in the NodeHosts section in CoreDNS, to make the names resolvable from within the cluster
  • Note: does not work in hostnetwork mode
• 💻 new Simple config option for aforementioned CLI flag

   hostAliases:
   	- ip: 1.2.3.4
   	  hostnames:
   		- foo.bar.baz
   		- my.host.local

  • Note: does not work in hostnetwork mode

Changed

• 🧰 hostname validation (e.g. for cluster and node names) now uses a Regexp to comply with RFC 1123)
• 🧰 New RewriteFileActionOpts with option NoCopy to work around "Resource Busy" issue, e.g. when overwriting /etc/hosts in containers
• 🧰 new field HostAliases in SimpleConfig, ClusterCreateOpts and ClusterStartOpts
• 🧰 new NewHostAliasesInjectEtcHostsAction function to easily create a new action to inject entries into /etc/hosts in k3d node containers

References

• fixes [FEATURE] extra_hosts or hostAliases in k3d config #813
• fixes [FEATURE] host.docker.internal resolving the same way as host.k3d.internal #884

Follow-Up To-Dos

• [FEATURE] add k3d cluster edit --host-alias flag #940

[iwilltry42]

Tests are not failing because of PR changes, so I'm merging this now ✔️

[m33ch]

Hi, thanks for this change! He saved me!
I point out that after creating the cluster and turning it off and on again the defined hosts are absent in coreDns configMap.
The only thing I can do is delete the cluester and recreate it.

Thanks

[karthick-kk]

is it possible to persist the defined hosts across stop/start of the cluster? it makes no sense if the changes are lost after a system reboot and to see none of the changes seem to exist.

[iwilltry42]

Persisting the changes across restarts is on the roadmap.
Due to the lack of contributors, it may take some time to land though.
Basically, the entries have to be re-injected on every start, as K3s overwrites them upon startup.

[m33ch]

Hi @iwilltry42,

looking at the cluster start code I noticed that host aliases injection is present, but apparently it doesn't work.
Is there a workaround so that i don't have to delete e create the cluster every time?

Thank you