bundles/systemd-swap: be reboot safe by initializing swap in another unit

bundles/systemd-swap/items.py

@@ -1,58 +1,13 @@
-size = node.metadata.get('systemd-swap')
-
-actions = {
-    'stop_swap': {
-        'command': f'systemctl stop swapfile.swap',
-        'unless': f'! systemctl is-active swapfile.swap',
-        'triggered': True,
-    },
-    'remove_swapfile': {
-        'command': f'rm /swapfile',
-        'unless': f'! test -e /swapfile',
-        'triggered': True,
-        'needs': {
-            'action:stop_swap',
-        },
-    },
-    'create_swapfile': {
-        'command': f'fallocate -l {size} /swapfile',
-        'unless': f'stat -c %s /swapfile | grep ^{size}$',
-        'preceded_by': {
-            'action:stop_swap',
-            'action:remove_swapfile',
-        },
-        'triggers': {
-            'action:initialize_swapfile',
-            'svc_systemd:swapfile.swap:restart',
-        },
-    },
-    'swapfile_mode': {
-        'command': f'chmod 600 /swapfile',
-        'unless': f'stat -c "%a" /swapfile | grep -q "^600$"',
-        'needs': {
-            'action:create_swapfile',
-        },
-        'triggers': {
-            'svc_systemd:swapfile.swap:restart',
-        },
-    },
-    'initialize_swapfile': {
-        'command': f'mkswap /swapfile',
-        'triggered': True,
-        'needs': {
-            'action:swapfile_mode',
-        }
-    },
-}
-
 svc_systemd = {
+    'swapfile-prepare.service': {
+        'enabled': True,
+        'running': None,
+    },
     'swapfile.swap': {
-        'preceded_by': {
+        'enabled': True,
-            'action:initialize_swapfile',
+        'running': True,
-        },
+        'needs': [
-        'needs': {
+            'svc_systemd:swapfile-prepare.service',
-            'action:initialize_swapfile',
+        ],
-            'action:systemd-reload',
-        },
     },
 }

bundles/systemd-swap/metadata.py

@@ -10,3 +10,38 @@ defaults = {
         },
     },
 }
+
+
+@metadata_reactor.provides(
+    'systemd/units/swapfile.swap',
+)
+def unit(metadata):
+    size = metadata.get('systemd-swap')
+
+    return {
+        'systemd': {
+            'units': {
+                'swapfile-prepare.service': {
+                    'Unit': {
+                        'Before': {
+                            'swapfile.swap',
+                        },
+                    },
+                    'Service': {
+                        'Type': 'oneshot',
+                        'ExecStartPre': [
+                            '-/bin/rm /swapfile -f',
+                            f'/bin/fallocate -l {size} /swapfile',
+                            '/bin/chmod 600 /swapfile',
+                        ],
+                        'ExecStart': '/usr/sbin/mkswap /swapfile',
+                    },
+                    'Install': {
+                        'RequiredBy': {
+                            'swapfile.swap',
+                        },
+                    },
+                },
+            },
+        },
+    }