mount_plugin: run zerofree by default on unmount

When unmounting `ext*` filesystems, run zerofree by default unless told
not to via a `zerofree: false` key

2 files changed, 14 insertions, 1 deletions

diff --git a/vmdb/plugins/mount.mdwn b/vmdb/plugins/mount.mdwn
index 9c830ef..b646fb3 100644
--- a/vmdb/plugins/mount.mdwn
+++ b/vmdb/plugins/mount.mdwn
@@ -12,6 +12,10 @@ Step keys:
 * `mount-on` — OPTIONAL; tag of already mounted filesystem in
   image. (FIXME: this may be wrong?)
 
+* `zerofree` — OPTIONAL; Boolean flag controlling whether or not to run
+  the `zerofree` utility on the filesystem after unmounting it at the end of
+  the build process. Defaults to `true`
+
 Example (in the .vmdb file):
 
     - mount: root
diff --git a/vmdb/plugins/mount_plugin.py b/vmdb/plugins/mount_plugin.py
index b8102a6..b18c009 100644
--- a/vmdb/plugins/mount_plugin.py
+++ b/vmdb/plugins/mount_plugin.py
@@ -30,13 +30,22 @@ class MountPlugin(vmdb.Plugin):
 
 class MountStepRunner(vmdb.StepRunnerInterface):
     def get_key_spec(self):
-        return {"mount": str, "dirname": "", "mount-on": ""}
+        return {"mount": str, "dirname": "", "mount-on": "", "zerofree": True}
 
     def run(self, values, settings, state):
         self.mount_rootfs(values, settings, state)
 
     def teardown(self, values, settings, state):
         self.unmount_rootfs(values, settings, state)
+        tag = values["mount"]
+        run_zerofree = values.get("zerofree", True)
+        if run_zerofree:
+            fstype = state.tags.get_fstype(tag)
+            if fstype.startswith('ext'):
+                dev = state.tags.get_dev(tag)
+                vmdb.runcmd(["zerofree", "-v", dev])
+            else:
+                logging.info(f"not running zerofree on {tag} with {fstype} filesystem")
 
     def mount_rootfs(self, values, settings, state):
         tag = values["mount"]