save snapshot of unmodified root before first mount

1 files changed, 6 insertions, 0 deletions

diff --git a/fsmgr.hs b/fsmgr.hs
index bfd3cb3..796863d 100644
--- a/fsmgr.hs
+++ b/fsmgr.hs
@@ -85,6 +85,12 @@ buildRoot DiskImageConfig{..} finalOut = do
     {- 4. custom setup commands -}
     forM_ chrootCommands $ \c -> do
       cmd_ "chroot" [mountpoint] "/bin/sh -c" [unpack c]
+    {- 5. create a backup snapshot -}
+    cmd_ "umount" [mountpoint]
+    cmd_ "mount -t btrfs -o subvol=/" [out, mountpoint]
+    flip actionCatch (\(SomeException _) -> return ()) $ cmd_ "btrfs subvolume delete" [mountpoint </> "root~orig"]
+    cmd_ "btrfs subvolume snapshot -r" [mountpoint </> "root", mountpoint </> "root~orig"]
+
     -- cleanup
     cmd_ "umount" [mountpoint]
     cmd_ "rmdir" [mountpoint]