I'm trying to deploy a small Django app, that creates its own db.sqlite3 database, in a Kubernetes pod. When doing so without a persistent volume to save the db.sqlite3, it works fine but when trying to save it in a persistent volume, the pod outputs django.db.utils.OperationalError: unable to open database file
The first problem I had is when these commands:
python ./manage.py migrate
sh -c "envdir ${ENVDIR} python manage.py collectstatic"
were run in the Dockerfile. After mounting the volume, none of my files would be visible. I learned that K8s volumes behaved differently from docker volumes and my solution was to put the commands in a shell script and execute it in the CMD or ENTYPOINT. This created the files after mounting and were visible but still doesn't help with the current problem.
I tried using a persistent volume, tried using a hostPath defined volume and even tried using an initContainer that has the same image as the app, only it first sets the permissions to 777 for db.sqlite3 and executes the two commands above, but it can't even start for some reason.
Here's the deployment.yaml:
apiVersion: apps/v1
kind: Deployment
metadata:
name: myapp
labels:
app: myapp
namespace: app-prod
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
securityContext:
runAsUser: 0
runAsGroup: 0
fsGroup: 0
fsGroupChangePolicy: "OnRootMismatch"
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: role
operator: In
values:
- on-demand-worker
terminationGracePeriodSeconds: 30
containers:
- name: notation
image: myimage
imagePullPolicy: Always
command: ["bash", "-c", "python ./manage.py runserver 0.0.0.0:8000"]
ports:
- containerPort: 8000
name: http
volumeMounts:
- name: myapp-data
mountPath: /app/db.sqlite3
subPath: db.sqlite3
securityContext:
privileged: true
#securityContext:
#allowPrivilegeEscalation: false
initContainers:
- name: sqlite-data-permission-fix
image: myimage
command: ["bash","-c","chmod -R 777 /app && python ./manage.py migrate && envdir ./notation/.devenv python manage.py collectstatic"]
volumeMounts:
- name: myapp-data
mountPath: /app/db.sqlite3
subPath: db.sqlite3
resources: {}
volumes:
- name: myapp-data
persistentVolumeClaim:
claimName: notation
The permissions I see on the host look good, 777 as I wanted them to be so I really don't know what the problem is... Any help would be appreciated.
Copyright Notice：Content Author:「Erokos」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/69703942/using-django-with-db-sqlite3-with-persistent-volume-in-a-kubernetes-pod-outputs