How to add extra hosts entries in helm charts - kubernetes

Question

So i'm deploying my application stack on kubernetes sing helm charts and now i need to add some dependant server ip's and hostnames inside my pods /etc/hosts file so need help on this scenario

Answer 1

A helm templated solution to the original question. I tested this with helm 3.
apiVersion: apps/v1
kind: Deployment
spec:
template:
spec:
{{- with .Values.hostAliases }}
hostAliases:
{{ toYaml . | indent 8 }}
{{- end }}
For values such as:
hostAliases:
- ip: "10.0.0.1"
hostnames:
- "host.domain.com"
If the hostAliases is omitted or commented out in the values, the hostAliases section is omitted when the template is rendered.

Answer 2

As standing in documentation you can add extra hosts to POD by using host aliases feature
Example from docs:
apiVersion: v1
kind: Pod
metadata:
name: hostaliases-pod
spec:
restartPolicy: Never
hostAliases:
- ip: "127.0.0.1"
hostnames:
- "foo.local"
- "bar.local"
- ip: "10.1.2.3"
hostnames:
- "foo.remote"
- "bar.remote"
containers:
- name: cat-hosts
image: busybox
command:
- cat
args:
- "/etc/hosts"

Answer 3

Kubernetes provides a DNS service that all pods get to use. In turn, you can define an ExternalName service that just defines a DNS record. Once you do that, your pods can talk to that service the same way they'd talk to any other Kubernetes service, and reach whatever server.
You could deploy a set of ExternalName services globally. You could do it in a Helm chart too, if you wanted, something like
apiVersion: v1
kind: Service
metadata:
name: {{ .Release.Name }}-{{ .Chart.Name }}-foo
spec:
type: ExternalName
externalName: {{ .Values.fooHostname }}
The practice I've learned is that you should avoid using /etc/hosts if at all possible.