2 min read | by Jordi Prats
The /etc/hosts file is a Kubernetes-managed file so we cannot add entries freely to it. If we want to add entries to it we will have to use the hostAliases field in the Pod's spec.
$ kubectl exec -it demo-pod -- cat /etc/hosts # Kubernetes-managed hosts file. 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet fe00::0 ip6-mcastprefix fe00::1 ip6-allnodes fe00::2 ip6-allrouters 10.103.198.74 demo-pod Adding entries on the pod's /etc/hosts comes really handy when we want to override some domains just for the given pod. To do so we just need to include the entry on the Pod's spec.
The /etc/hosts format is the following:
IP_address canonical_hostname [aliases...] The hostAliases format allows us to define as many aliases as we want using the hostnames array:
apiVersion: v1 kind: Pod metadata: name: demo-pod spec: containers: - command: - sh - /code/apply.sh image: alpine name: demo hostAliases: - hostnames: - example.pet2cattle.com ip: 1.2.3.4 Checking on the running pod we will see how it generates the following /etc/hosts file:
$ kubectl exec -it demo-pod -- cat /etc/hosts # Kubernetes-managed hosts file. 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet fe00::0 ip6-mcastprefix fe00::1 ip6-allnodes fe00::2 ip6-allrouters 10.103.198.74 demo-pod # Entries added by HostAliases. 1.2.3.4 example.pet2cattle.com For more details you can check the kubernetes documenentation about hostAliases
Posted on 11/05/2021