fix: prevent creation of clones after reverting to previous snap revision

snap/hooks/configure

@@ -36,15 +36,14 @@ config_entries = [
     ("flush-interval", "flush_interval", None),
     ("exchange-interval", "exchange_interval", None),
     ("apt-update-interval", "apt_update_interval", None),
-    ("exchange-interval", "exchange_interval", None),
     ("cloud", "cloud", None),
 ]
 
 changed = set()
 for snapctl_key, landscape_key, mapping_fn in config_entries:
     value = _snapctl("get", snapctl_key).strip()
     if not value:
-        # empty, value not has not changed
+        # empty, value has not changed
         continue
 
     if mapping_fn:

snap/hooks/post-refresh

@@ -0,0 +1,26 @@
+#!/bin/sh -e
+
+# This hook migrates the client's data from $SNAP_DATA to $SNAP_COMMON.
+# It will be kept until all the existing
+#  clients are migrated to $SNAP_COMMON (using this hook).
+# Full bug report: https://bugs.launchpad.net/landscape-client/+bug/2082616
+
+OLD_DIR="$SNAP_DATA/var/lib/landscape/client"
+NEW_DIR="$SNAP_COMMON/var/lib/landscape/client"
+
+# Is a migration needed? We check if:
+#  1. $OLD_DIR exists
+#  2. And that we've not already done the migration
+if [ -d "$OLD_DIR" ] && [ ! -f "$NEW_DIR/.migrated" ]; then
+   # Copy files while preserving attributes, links, etc
+   cp -a "$OLD_DIR/." "$NEW_DIR/"
+
+   # Flush file system buffers, ensuring all pending writes are completed
+   sync
+
+   # Add migration completion marker
+   touch "$NEW_DIR/.migrated"
+
+   # Remove the old directory
+   rm -rf "$OLD_DIR"
+fi

snap/snapcraft.yaml

@@ -10,7 +10,7 @@ description: |
   in a Landscape account. It provides the Landscape client and requires a
   Landscape account.
 
-grade: stable # must be 'stable' to release into candidate/stable channels
+grade: stable
 architectures:
   - build-on: [amd64]
   - build-on: [arm64]
@@ -33,7 +33,7 @@ slots:
   annotations:
     interface: content
     write:
-      - $SNAP_DATA/var/lib/landscape/client/annotations.d
+      - $SNAP_COMMON/var/lib/landscape/client/annotations.d
 
 apps:
   landscape-client:
@@ -61,11 +61,21 @@ apps:
     plugs:
       - network
       - hardware-observe
+
+# Previously, the client's data was stored in $SNAP_DATA
+#  which led to duplicate machine entries after reverting
+#  to a previous revision.
+# After the migration of /var/lib/landscape/client from
+#  $SNAP_DATA to $SNAP_COMMON, the snap's layout changed.
+# The new epoch 1* means the snap can read the previous
+#  & new epochs' data but can only write epoch 1 data.
+epoch: 1*
+
 layout:
   /etc/landscape-client.conf:
     bind-file: $SNAP_COMMON/etc/landscape-client.conf
   /var/lib/landscape/client:
-    bind: $SNAP_DATA/var/lib/landscape/client
+    bind: $SNAP_COMMON/var/lib/landscape/client
   /var/log/landscape:
     bind: $SNAP_DATA/var/log/landscape