Kubernetes Persistant Volume overwrites image data
I have a pod that reads from an image that contains data within var/www/html. I want this data to be stored in a persistent volume. This is my deployment yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
name: app
spec:
replicas: 1
selector:
matchLabels:
container: app
template:
metadata:
labels:
container: app
spec:
containers:
- name: app
image: my/toolkit-app:working
ports:
- containerPort: 80
volumeMounts:
- mountPath: /var/www/html
name: toolkit-volume
subPath: html
volumes:
- name: toolkit-volume
persistentVolumeClaim:
claimName: azurefile
imagePullSecrets:
- name: my-credHowever when I look into the pod I can see the directory is empty:
If I comment out the persistent volume:
#volumeMounts:
# - mountPath: /var/www/html
# name: toolkit-volume
# subPath: htmlI can see that the image data is there:
So it seems like the persistent volume is overwriting the existing directory - is there a way round this? Ideally I want /var/www/html to be stored in a separate volume and for any existing files within the image to be stored there too.
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1 Answer
This is more a problem of visibility: If you mount an empty volume at a specific path, you won't be able to see, what was placed there in the container image.
From your question I assume that you want to be able to rollout updates by the means of a new container image, but at the same time retain variable data, that was created at the same directory from your application.
You could achieve this with the following method:
Use an init container with the same image and mount your persistent directory to a different path, for example /data
As command for the init container copy the contents of /var/www/html to /data.
In the regular container image use the mount you already have, it will contain your variable data and the updated data from the init container.