diff --git a/b9.cabal b/b9.cabal
--- a/b9.cabal
+++ b/b9.cabal
@@ -1,5 +1,5 @@
 name:                b9
-version:             0.5.46
+version:             0.5.47
 
 synopsis:            A tool and library for building virtual machine images.
 
diff --git a/src/cli/Main.hs b/src/cli/Main.hs
--- a/src/cli/Main.hs
+++ b/src/cli/Main.hs
@@ -78,6 +78,13 @@
                 )
         <*> optional
                 ( strOption
+                    (  help "Output file for a command/timing profile"
+                    <> long "profile-file"
+                    <> metavar "FILENAME"
+                    )
+                )
+        <*> optional
+                ( strOption
                     (  help
                           "Root directory for build directories. If not specified '.'. The path will be canonicalized and stored in ${buildDirRoot}."
                     <> short 'b'
@@ -116,12 +123,13 @@
         -> Bool
         -> Maybe FilePath
         -> Maybe FilePath
+        -> Maybe FilePath
         -> Bool
         -> Bool
         -> Maybe FilePath
         -> Maybe String
         -> B9ConfigOverride
-    toGlobalOpts cfg verbose quiet logF buildRoot keep notUnique mRepoCache repo
+    toGlobalOpts cfg verbose quiet logF profF buildRoot keep notUnique mRepoCache repo
         = let minLogLevel = if verbose
                   then Just LogTrace
                   else if quiet then Just LogError else Nothing
@@ -131,6 +139,8 @@
                       .~ minLogLevel
                       &  logFile
                       .~ logF
+                      &  profileFile
+                      .~ profF
                       &  buildDirRoot
                       .~ buildRoot
                       &  keepTempDirs
diff --git a/src/lib/B9/ArtifactGenerator.hs b/src/lib/B9/ArtifactGenerator.hs
--- a/src/lib/B9/ArtifactGenerator.hs
+++ b/src/lib/B9/ArtifactGenerator.hs
@@ -179,7 +179,7 @@
 getArtifactSourceFiles (FromContent   f _) = [f]
 getArtifactSourceFiles (FromFile      f _) = [f]
 getArtifactSourceFiles (IntoDirectory pd as) =
-    (pd </>) <$> (as >>= getArtifactSourceFiles)
+    (pd</>) <$> (as >>= getArtifactSourceFiles)
 getArtifactSourceFiles (FromDirectory _ as) = as >>= getArtifactSourceFiles
 getArtifactSourceFiles (SetPermissions _ _ _ as) =
     as >>= getArtifactSourceFiles
@@ -275,11 +275,11 @@
 getAssemblyOutput (VmImages ts _) =
     AssemblyGeneratesOutputFiles . getImageDestinationOutputFiles <$> ts
 getAssemblyOutput (CloudInit ts o) = getCloudInitOutputFiles o <$> ts
-  where
-    getCloudInitOutputFiles baseName t = case t of
-        CI_ISO  -> AssemblyGeneratesOutputFiles [baseName <.> "iso"]
-        CI_VFAT -> AssemblyGeneratesOutputFiles [baseName <.> "vfat"]
-        CI_DIR  -> AssemblyCopiesSourcesToDirectory baseName
+ where
+  getCloudInitOutputFiles baseName t = case t of
+      CI_ISO  -> AssemblyGeneratesOutputFiles [baseName <.> "iso"]
+      CI_VFAT -> AssemblyGeneratesOutputFiles [baseName <.> "vfat"]
+      CI_DIR  -> AssemblyCopiesSourcesToDirectory baseName
 
 
 -- * QuickCheck instances
@@ -297,21 +297,21 @@
 
 arbitraryEachT :: Gen ([ArtifactGenerator] -> ArtifactGenerator)
 arbitraryEachT =
-    sized
-        $ \n ->
-              EachT
-                  <$> vectorOf n (halfSize (listOf1 (choose ('a', 'z'))))
-                  <*> oneof
-                          [ listOf (vectorOf n (halfSize arbitrary))
-                          , listOf1 (listOf (halfSize arbitrary))
-                          ]
+    sized $
+    \n ->
+         EachT <$> vectorOf n (halfSize (listOf1 (choose ('a', 'z')))) <*>
+         oneof
+             [ listOf (vectorOf n (halfSize arbitrary))
+             , listOf1 (listOf (halfSize arbitrary))]
 
 arbitraryEach :: Gen ([ArtifactGenerator] -> ArtifactGenerator)
-arbitraryEach = sized $ \n -> Each <$> listOf
-    ( (,) <$> listOf1 (choose ('a', 'z')) <*> vectorOf
-        n
-        (halfSize (listOf1 (choose ('a', 'z'))))
-    )
+arbitraryEach =
+    sized $
+    \n ->
+         Each <$>
+         listOf
+             ((,) <$> listOf1 (choose ('a', 'z')) <*>
+              vectorOf n (halfSize (listOf1 (choose ('a', 'z')))))
 
 
 instance Arbitrary ArtifactSource where
@@ -336,4 +336,3 @@
 
 instance Arbitrary CloudInitType where
     arbitrary = elements [CI_ISO, CI_VFAT, CI_DIR]
-
diff --git a/src/lib/B9/B9Config.hs b/src/lib/B9/B9Config.hs
--- a/src/lib/B9/B9Config.hs
+++ b/src/lib/B9/B9Config.hs
@@ -8,6 +8,7 @@
                    , buildDirRoot
                    , keepTempDirs
                    , execEnvType
+                   , profileFile
                    , envVars
                    , uniqueBuildDirs
                    , repositoryCache
@@ -80,6 +81,7 @@
                          , _buildDirRoot :: Maybe FilePath
                          , _keepTempDirs :: Bool
                          , _execEnvType :: ExecEnvType
+                         , _profileFile :: Maybe FilePath
                          , _envVars :: BuildVariables
                          , _uniqueBuildDirs :: Bool
                          , _repositoryCache :: Maybe SystemPath
@@ -97,6 +99,7 @@
       , _buildDirRoot = getLast $ on mappend (Last . _buildDirRoot) c c'
       , _keepTempDirs = getAny $ on mappend (Any . _keepTempDirs) c c'
       , _execEnvType = LibVirtLXC
+      , _profileFile = getLast $ on mappend (Last . _profileFile) c c'
       , _envVars = on mappend _envVars c c'
       , _uniqueBuildDirs = getAll ((mappend `on` (All . _uniqueBuildDirs)) c c')
       , _repositoryCache = getLast $ on mappend (Last . _repositoryCache) c c'
@@ -109,7 +112,7 @@
 
 instance Monoid B9Config where
   mappend = (Sem.<>)
-  mempty = B9Config Nothing Nothing Nothing False LibVirtLXC [] True
+  mempty = B9Config Nothing Nothing Nothing False LibVirtLXC Nothing [] True
                     Nothing Nothing False Nothing Nothing []
 
 -- | Override b9 configuration items and/or the path of the b9 configuration file.
@@ -261,6 +264,7 @@
   , _buildDirRoot                 = Nothing
   , _keepTempDirs                 = False
   , _execEnvType                  = LibVirtLXC
+  , _profileFile                  = Nothing
   , _envVars                      = []
   , _uniqueBuildDirs              = True
   , _repository                   = Nothing
@@ -285,6 +289,8 @@
 keepTempDirsK = "keep_temp_dirs"
 execEnvTypeK :: String
 execEnvTypeK = "exec_env"
+profileFileK :: String
+profileFileK = "profile_file"
 envVarsK :: String
 envVarsK = "environment_vars"
 uniqueBuildDirsK :: String
@@ -314,21 +320,22 @@
   cp4 <- setShowCP cp3 cfgFileSection buildDirRootK (_buildDirRoot c)
   cp5 <- setShowCP cp4 cfgFileSection keepTempDirsK (_keepTempDirs c)
   cp6 <- setShowCP cp5 cfgFileSection execEnvTypeK (_execEnvType c)
-  cp7 <- setShowCP cp6 cfgFileSection envVarsK (_envVars c)
-  cp8 <- setShowCP cp7 cfgFileSection uniqueBuildDirsK (_uniqueBuildDirs c)
-  cp9 <- setShowCP cp8
+  cp7 <- setShowCP cp6 cfgFileSection profileFileK (_profileFile c)
+  cp8 <- setShowCP cp7 cfgFileSection envVarsK (_envVars c)
+  cp9 <- setShowCP cp8 cfgFileSection uniqueBuildDirsK (_uniqueBuildDirs c)
+  cpA <- setShowCP cp9
                    cfgFileSection
                    maxLocalSharedImageRevisionsK
                    (_maxLocalSharedImageRevisions c)
-  cpA <- setShowCP cp9 cfgFileSection repositoryCacheK (_repositoryCache c)
-  cpB <-
+  cpB <- setShowCP cpA cfgFileSection repositoryCacheK (_repositoryCache c)
+  cpC <-
     ( foldr (>=>)
             return
             (libVirtLXCConfigToCPDocument <$> (_libVirtLXCConfigs c))
       )
-      cpA
+      cpB
   cpFinal <- (foldr (>=>) return (remoteRepoToCPDocument <$> _remoteRepos c))
-    cpB
+    cpC
   setShowCP cpFinal cfgFileSection repositoryK (_repository c)
 
 readB9Config :: MonadIO m => Maybe SystemPath -> m CPDocument
@@ -346,6 +353,7 @@
         <*> getr buildDirRootK
         <*> getr keepTempDirsK
         <*> getr execEnvTypeK
+        <*> getr profileFileK
         <*> getr envVarsK
         <*> getr uniqueBuildDirsK
         <*> getr repositoryCacheK
diff --git a/src/lib/B9/B9Monad.hs b/src/lib/B9/B9Monad.hs
--- a/src/lib/B9/B9Monad.hs
+++ b/src/lib/B9/B9Monad.hs
@@ -45,9 +45,17 @@
              ,bsLogFileHandle :: Maybe SysIO.Handle
              ,bsSelectedRemoteRepo :: Maybe RemoteRepo
              ,bsRepoCache :: RepoCache
+             ,bsProf :: [ProfilingEntry]
              ,bsStartTime :: UTCTime
              ,bsInheritStdIn :: Bool}
 
+data ProfilingEntry
+  = IoActionDuration NominalDiffTime
+  | LogEvent LogLevel
+             String
+  deriving (Eq,Show)
+
+
 run :: MonadIO m => B9 a -> B9ConfigAction m a
 run action = do
   cfg <- askRuntimeConfig
@@ -92,6 +100,7 @@
                        logFileHandle
                        selectedRemoteRepo
                        repoCache
+                       []
                        now
                        (_interactive finalCfg)
       selectedRemoteRepo = do
@@ -103,6 +112,10 @@
             (show remoteRepos')
           )
     (r, ctxOut) <- runStateT (runB9 wrappedAction) ctx
+    -- Write a profiling report
+    when (isJust (_profileFile cfg)) $ writeFile
+      (fromJust (_profileFile cfg))
+      (unlines $ show <$> reverse (bsProf ctxOut))
     return r
   createBuildDir cfg buildId = if _uniqueBuildDirs cfg
     then do
@@ -159,6 +172,22 @@
 getRepoCache :: B9 RepoCache
 getRepoCache = gets bsRepoCache
 
+-- getDownloader :: B9 Downloader
+-- getDownloader = gets bsDownloader
+--
+-- -- | Configuration for a tool that retreives arbitrary URL and returns them to
+-- -- @stdout@.
+-- data Downloader =
+--   Downloader {downloaderCmd :: FilePath
+--              ,downloaderArgsBeforeUrl :: [String]
+--              ,downloaderUrlArgPrintfFormatString :: [String]
+--              ,downloaderArgsAfterUrl :: [String]}
+--   deriving (Read,Show,Eq,Ord,Typeable,Generic)
+--
+-- readContentFromUrl :: String -> B9 B.ByteString
+-- readContentFromUrl url = do
+--   return expression
+
 cmd :: String -> B9 ()
 cmd str = do
   inheritStdIn <- gets bsInheritStdIn
@@ -217,6 +246,7 @@
 b9Log level msg = do
   lv  <- gets $ _verbosity . bsCfg
   lfh <- gets bsLogFileHandle
+  modify $ \ctx -> ctx { bsProf = LogEvent level msg : bsProf ctx }
   B9 $ liftIO $ logImpl lv lfh level msg
 
 logImpl :: Maybe LogLevel -> Maybe SysIO.Handle -> LogLevel -> String -> IO ()
@@ -246,4 +276,10 @@
   deriving (Functor,Applicative,Monad,MonadState BuildState)
 
 instance MonadIO B9 where
-  liftIO m = B9 $ liftIO m
+  liftIO m =
+    do start <- B9 $ liftIO getCurrentTime
+       res <- B9 $ liftIO m
+       stop <- B9 $ liftIO getCurrentTime
+       let durMS = IoActionDuration (stop `diffUTCTime` start)
+       modify $ \ctx -> ctx {bsProf = durMS : bsProf ctx}
+       return res