track devices in multi-device btrfs images, in file *.btrfs.devices.txt

1 files changed, 11 insertions, 0 deletions

diff --git a/fsmgr.hs b/fsmgr.hs
index 257b56c..2f3e0f5 100644
--- a/fsmgr.hs
+++ b/fsmgr.hs
@@ -25,6 +25,7 @@ import qualified Options.Applicative        as Opt
 
 import           ConfigFile
 import           String
+import           System.Directory           as IO
 import           System.Directory           (createDirectoryIfMissing,
                                              getCurrentDirectory)
 import           System.Posix.Process       (getProcessID)
@@ -126,6 +127,11 @@ getHomeDir = do
   Stdout homeDir <- cmd "sh -c" ["if [ \"$SUDO_USER\" ]; then getent passwd \"$SUDO_USER\" | cut -d: -f6; else printf \"%s\n\" \"$HOME\"; fi"]
   return homeDir
 
+readFileOptional :: FilePath -> IO (String)
+readFileOptional f = IO.doesFileExist f >>= \case
+  True -> readFile f
+  False -> return ""
+
 buildInitialImage :: DiskImageConfig -> FilePath -> FilePath -> Action ()
 buildInitialImage DiskImageConfig{..} mountpoint out = do
   case initialImage of
@@ -135,12 +141,17 @@ buildInitialImage DiskImageConfig{..} mountpoint out = do
       cmd_ "cp --reflink" [parent, out]
       cmd_ "btrfstune -f -S0" [out]
       cmd_ "mkdir -p" [mountpoint]
+      cmd_ "sh -c" ["if [ -e \"$0\" ]; then cp \"$0\" \"$1\"; fi", parent <.> "devices.txt", out -<.> "devices.txt"]
+
       cmd_ "mount -t btrfs" [out] mountpoint
 
     SeededImage n f -> do
       let parent = "_build" </> f -<.> "btrfs"
       need [parent]
 
+      devices <- either (const []) lines . readEither <$> liftIO (readFileOptional (parent <.> "devices.txt"))
+      writeFile' (out -<.> "devices.txt") (unlines $ parent:devices)
+
       -- allocate new image file
       cmd_ "rm -f" [out]
       cmd_ "truncate -s" [show n, out]