How to change, edit, save /etc/hosts file from Azure Bash for Kubernetes? - linux

Question

I uploaded a project to kubernetes and for its gateway to redirect the services, it requires the following:
127.0.0.1 app.my.project
127.0.0.1 event-manager.my.project
127.0.0.1 logger.my.project
and so on.
I can't run any sudo commands, so sudo nano /etc/hosts doesnt work. I tried vi /etc/hosts and it gives permission denied error. How can I edit /etc/hosts file or do some configuration on Azure to make it work like that?
Edit:
To give more information, I have uploaded a project to Kubernetes that has reverse-proxy settings.
So reaching the web-app of that project is not available via IP. Instead if I'm running the application locally, I have to edit the hosts file of the computer I'm using with
127.0.0.1 app.my.project
127.0.0.1 event-manager.my.project
127.0.0.1 logger.my.project
and so on. So whenever I type web-app.my.project its gateway redirects to web-app part and if I write app.my.project it redirects to app part, etc.
When I uploaded it to Azure Kubernetes Service it added default-http-backend on ingress-nginx namespace which created by itself. To expose these services, I opened the Http Routing option from Azure which gave me the loadbalancer at the left side of the image. So If I'm reading the situation correctly, (I'm most probably wrong though) it is something like the image below:
So, I added hostaliases to kube-system, ingress-nginx and default namespaces to make it like I edited a hosts file when I was running the project locally. But it still gives me that default backend - 404 ingress error
Edit 2:
I have nginx-ingress-controller which allows the redirection as far as I understand. So, when I add hostaliases to it as follows:
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-ingress-controller
namespace: ingress-nginx
spec:
replicas: 1
selector:
matchLabels:
app: ingress-nginx
template:
metadata:
labels:
app: ingress-nginx
annotations:
prometheus.io/port: '10254'
prometheus.io/scrape: 'true'
spec:
hostAliases:
- ip: "127.0.0.1"
hostnames:
- "app.ota.local"
- "gateway.ota.local"
- "treehub.ota.local"
- "tuf-reposerver.ota.local"
- "web-events.ota.local"
hostNetwork: true
serviceAccountName: nginx-ingress-serviceaccount
containers:
- name: nginx-ingress-controller
image: {{ .ingress_controller_docker_image }}
args:
- /nginx-ingress-controller
- --default-backend-service=$(POD_NAMESPACE)/default-http-backend
- --configmap=$(POD_NAMESPACE)/nginx-configuration
- --tcp-services-configmap=$(POD_NAMESPACE)/tcp-services
- --udp-services-configmap=$(POD_NAMESPACE)/udp-services
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
ports:
- name: tcp
containerPort: 8000
- name: http
containerPort: 80
- name: https
containerPort: 443
livenessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
initialDelaySeconds: 10
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
readinessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 10254
scheme: HTTP
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 1
So when I edit yaml file as aforementioned, it gives the following error on Azure:
Failed to update the deployment
Failed to update the deployment 'nginx-ingress-controller'. Error: BadRequest (400) : Deployment in version "v1" cannot be handled as a Deployment: v1.Deployment.Spec: v1.DeploymentSpec.Template: v1.PodTemplateSpec.Spec: v1.PodSpec.HostAliases: []v1.HostAlias: readObjectStart: expect { or n, but found ", error found in #10 byte of ...|liases":["ip "127.0|..., bigger context ...|theus.io/scrape":"true"}},"spec":{"hostAliases":["ip "127.0.0.1""],"hostnames":["app.ota.local","g|...
If I edit the yaml file locally and try to run it from local kubectl which is connected to Azure, it gives the following error:
serviceaccount/weave-net configured
clusterrole.rbac.authorization.k8s.io/weave-net configured
clusterrolebinding.rbac.authorization.k8s.io/weave-net configured
role.rbac.authorization.k8s.io/weave-net configured
rolebinding.rbac.authorization.k8s.io/weave-net configured
daemonset.apps/weave-net configured Using cluster from kubectl
context: k8s_14
namespace/ingress-nginx unchanged deployment.apps/default-http-backend
unchanged service/default-http-backend unchanged
configmap/nginx-configuration unchanged configmap/tcp-services
unchanged configmap/udp-services unchanged
serviceaccount/nginx-ingress-serviceaccount unchanged
clusterrole.rbac.authorization.k8s.io/nginx-ingress-clusterrole
unchanged role.rbac.authorization.k8s.io/nginx-ingress-role unchanged
rolebinding.rbac.authorization.k8s.io/nginx-ingress-role-nisa-binding
unchanged
clusterrolebinding.rbac.authorization.k8s.io/nginx-ingress-clusterrole-nisa-binding
unchanged error: error validating
"/home/.../ota-community-edition/scripts/../generated/templates/ingress":
error validating data: ValidationError(Deployment.spec.template.spec):
unknown field "hostnames" in io.k8s.api.core.v1.PodSpec; if you choose
to ignore these errors, turn validation off with --validate=false
make: *** [Makefile:34: start_start-all] Error 1

Answer 1

Adding entries to a
Pod's /etc/hosts file provides Pod-level override of hostname
resolution when DNS and other options are not applicable. You can add
these custom entries with the HostAliases field in PodSpec.
Modification not using HostAliases is not suggested because the file
is managed by the kubelet and can be overwritten on during Pod
creation/restart.
I suggest that you use hostAliases instead
apiVersion: v1
kind: Pod
metadata:
name: hostaliases-pod
spec:
restartPolicy: Never
hostAliases:
- ip: "127.0.0.1"
hostnames:
- "app.my.project"
- "event-manager.my.project"
- "logger.my.project"
containers:
- name: cat-hosts
image: busybox
command:
- cat
args:
- "/etc/hosts"