Is it possible to use a bash script to do the liveness test in pod? - kubernetes

Question

I'm currently setting up a kubernetes cluster with 3 nodes on 3 differents vm and each node is composed of 1 pod witch run the following docker image: ethereum/client-go:stable
The problem is that I want to do a health check test using a bash script (because I have to test a lot of things) but I don't understand how I can export this file to each container that are deployed with my yaml deployment file.
I've tried to add wget command in the yaml file to download my health check script from my github repo but it wasn't very clean from my point of view, maybe there is an other way ?
My current deployment file:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: goerli
name: goerli-deploy
spec:
replicas: 3
selector:
matchLabels:
app: goerli
template:
metadata:
labels:
app: goerli
spec:
containers:
- image: ethereum/client-go:stable
name: goerli-geth
args: ["--goerli", "--datadir", "/test2"]
env:
- name: LASTBLOCK
value: "0"
- name: FAILCOUNTER
value: "0"
ports:
- containerPort: 30303
name: geth
livenessProbe:
exec:
command:
- /bin/sh
- /test/health.sh
initialDelaySeconds: 60
periodSeconds: 100
volumeMounts:
- name: test
mountPath: /test
restartPolicy: Always
volumes:
- name: test
hostPath:
path: /test
I expect to put health check script in /test/health.sh
Any ideas ?

Answer 1

This could be a perfect usecase for the init container, As there could be different images for the init container and the Application container thus they have different file system inside the pods, therefore we need to use Emptydir in order to share the state.
for further detail follow the link init-containers

Answer 2

Thanks to Suresh Vishnoi:
A way to resolve my problem is to use init container this way:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: goerli
name: goerli-deploy
spec:
replicas: 3
selector:
matchLabels:
app: goerli
template:
metadata:
labels:
app: goerli
spec:
containers:
- image: ethereum/client-go:stable
name: goerli-geth
args: ["--goerli", "--datadir", "/test2"]
env:
- name: LASTBLOCK
value: "0"
- name: FAILCOUNTER
value: "0"
ports:
- containerPort: 30303
name: geth
livenessProbe:
exec:
command:
- /bin/sh
- /test/health.sh
initialDelaySeconds: 60
periodSeconds: 100
volumeMounts:
- name: test
mountPath: /test
initContainers:
- name: healthcheck
image: ethereum/client-go:stable
command: ["wget", "-O", "/test2/health.sh", "https://My-script-bash"]
volumeMounts:
- name: test
mountPath: "/test"
restartPolicy: Always
volumes:
- name: test
emptyDir: {}
The downloaded file will be visible in /test/health.sh

Answer 3

If you're using helm look at chart tests: https://github.com/helm/helm/blob/master/docs/chart_tests.md. This covers readinessProbe tho, not liveness.
For advanced liveness probe, I'd run some kind of healthcheck sidecar which does all the advanced tests continiosly via localhost, and exposes a single /healthcheck endpoint. Then use the endpoint in a liveness probe.