Persist /etc/frepple in the Kubernetes manifest so runtime config survives pod restarts

contrib/kubernetes/frepple-deployment.yaml

@@ -23,6 +23,18 @@ spec:
       storage: 50Mi
 status: {}
 ---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: config-frepple
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 50Mi
+status: {}
+---
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -42,6 +54,26 @@ spec:
       labels:
         app: frepple
     spec:
+      initContainers:
+        # Seed /etc/frepple from the image on the first start only. The volume is
+        # mounted here at /mnt/config (not /etc/frepple) so the image's own copy
+        # stays visible to copy from; on later starts the file already exists and
+        # the copy is skipped, preserving runtime changes to djangosettings.py.
+        # Runs as root: the freshly provisioned volume root is root-owned, so a
+        # non-root user can't populate it, and cp -a can't preserve the image's
+        # root-owned files unless it runs as root. This replicates the image's
+        # ownership/modes (/etc/frepple is group-writable by the frepple group).
+        - name: seed-config
+          image: ghcr.io/frepple/frepple-community:latest
+          securityContext:
+            runAsUser: 0
+          command:
+            - sh
+            - -c
+            - test -f /mnt/config/djangosettings.py || cp -a /etc/frepple/. /mnt/config/
+          volumeMounts:
+            - mountPath: /mnt/config
+              name: config-frepple
       containers:
         - env:
             - name: POSTGRES_HOST
@@ -66,12 +98,17 @@ spec:
               cpu: 250m
               memory: "4294967296"
           volumeMounts:
+            - mountPath: /etc/frepple
+              name: config-frepple
             - mountPath: /var/log/apache2
               name: log-apache
             - mountPath: /var/log/frepple
               name: log-frepple
       restartPolicy: Always
       volumes:
+        - name: config-frepple
+          persistentVolumeClaim:
+            claimName: config-frepple
         - name: log-apache
           persistentVolumeClaim:
             claimName: log-apache

doc/installation-guide/advanced/kubernetes.rst

@@ -19,7 +19,20 @@ The following resources are then defined in your cluster:
 
 - A postgresql service to store the frepple data.
 
-- Persistent volumes to store the web server logs (50MB), the application logs (100MB)
-  and the postgresql data (1GB).
+- Persistent volumes to store the web server logs (50MB), the application logs (100MB),
+  the frepple configuration in ``/etc/frepple`` (50MB) and the postgresql data (1GB).
 
 - A network policy to keep the connection between frepple and its postgres database private.
+
+frepple stores its runtime configuration in ``/etc/frepple/djangosettings.py``: the
+Django secret key, the list of installed apps, the number of scenarios and some display
+settings are all written to this file as you use the application. The deployment therefore
+mounts ``/etc/frepple`` on a persistent volume, seeded from the image on the first start by
+an init container, so that this configuration survives pod restarts - the same way the
+docker-compose deployment persists it on a named volume. Without it the directory resets to
+the image defaults on every restart: a new secret key is generated (invalidating sessions),
+and installed apps and scenario settings are lost.
+
+The volume is seeded only once. After upgrading to a newer frepple image, any new default
+settings shipped in the image are not copied over an existing ``djangosettings.py``; review
+and apply such changes manually after an upgrade.