call dpkg only once for many debs

1 files changed, 3 insertions, 3 deletions

diff --git a/fsmgr.hs b/fsmgr.hs
index 894bd29..cc44796 100644
--- a/fsmgr.hs
+++ b/fsmgr.hs
@@ -56,9 +56,9 @@ buildRoot config@DiskImageConfig{..} finalOut = do
       -- "Required" even if no packages are specified. When there is a parent,
       -- assume that this has already happened.
       cmd_ "selfstrap --skip-update" (("--unpack" `consWhen` unpackOnly) ["-t", mountpoint]) packageNames
-    forM_ debs $ \pkg -> do cmd_ (AddEnv "DEBIAN_FRONTEND" "noninteractive")
-                                 ["dpkg"] [if unpackOnly then "--unpack" else "--install"]
-                                          ["--root", mountpoint, pkg]
+    when (not $ null debs) $ do
+      cmd_ (AddEnv "DEBIAN_FRONTEND" "noninteractive")
+           ["dpkg"] [if unpackOnly then "--unpack" else "--install"] debs
     {- 2.5. install apt package cache -}
     -- TODO
     {- 3. binaries -}