diff --git a/Annex/Content.hs b/Annex/Content.hs
index 15d58e2e26..638390b2bf 100644
--- a/Annex/Content.hs
+++ b/Annex/Content.hs
@@ -276,8 +276,7 @@ winLocker :: (LockFile -> IO (Maybe LockHandle)) -> ContentLocker
 winLocker takelock _ (Just lockfile) = 
 	let lck = do
 		modifyContentDir lockfile $
-			void $ liftIO $ tryIO $
-				writeFile (fromOsPath lockfile) ""
+			void $ liftIO $ tryIO $ writeFileString lockfile ""
 		liftIO $ takelock lockfile
 	in (lck, Nothing)
 -- never reached; windows always uses a separate lock file
@@ -991,7 +990,7 @@ withTmpWorkDir key action = do
 	-- clean up gitAnnexTmpWorkDir for those it finds.
 	obj <- prepTmp key
 	unlessM (liftIO $ doesFileExist obj) $ do
-		liftIO $ writeFile (fromOsPath obj) ""
+		liftIO $ writeFileString  obj ""
 		setAnnexFilePerm obj
 	let tmpdir = gitAnnexTmpWorkDir obj
 	createAnnexDirectory tmpdir
@@ -1083,7 +1082,7 @@ writeContentRetentionTimestamp key rt t = do
 		readContentRetentionTimestamp rt >>= \case
 			Just ts | ts >= t -> return ()
 			_ -> replaceFile (const noop) rt $ \tmp ->
-				liftIO $ writeFile (fromOsPath tmp) $ show t
+				liftIO $ writeFileString tmp $ show t
   where
 	lock = takeExclusiveLock
 	unlock = liftIO . dropLock
diff --git a/Annex/Fixup.hs b/Annex/Fixup.hs
index 1e245668f3..c6b1bf5042 100644
--- a/Annex/Fixup.hs
+++ b/Annex/Fixup.hs
@@ -1,6 +1,6 @@
 {- git-annex repository fixups
  -
- - Copyright 2013-2020 Joey Hess <id@joeyh.name>
+ - Copyright 2013-2025 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -9,29 +9,14 @@
 
 module Annex.Fixup where
 
+import Common
 import Git.Types
 import Git.Config
 import Types.GitConfig
-import Utility.Path
-import Utility.Path.AbsRel
-import Utility.SafeCommand
-import Utility.Directory
-import Utility.Exception
-import Utility.Monad
-import Utility.SystemDirectory
-import Utility.OsPath
 import qualified Utility.RawFilePath as R
-import Utility.PartialPrelude
 import qualified Utility.OsString as OS
 
-import System.IO
-import Data.List
-import Data.Maybe
-import Control.Monad
-import Control.Monad.IfElse
 import qualified Data.Map as M
-import Control.Applicative
-import Prelude
 
 fixupRepo :: Repo -> GitConfig -> IO Repo
 fixupRepo r c = do
@@ -132,11 +117,11 @@ fixupUnusualRepos r@(Repo { location = Local { worktree = Just w, gitdir = d } }
 	-- git-worktree sets up a "commondir" file that contains
 	-- the path to the main git directory.
 	-- Using --separate-git-dir does not.
-	commondirfile = fromOsPath (d </> literalOsPath "commondir")
+	commondirfile = d </> literalOsPath "commondir"
 	
 	readcommondirfile = catchDefaultIO Nothing $
 		fmap toOsPath . headMaybe . lines
-			<$> readFile commondirfile
+			<$> readFileString commondirfile
 
 	setworktreepath r' = readcommondirfile >>= \case
 		Just gd -> return $ r'
diff --git a/Annex/Path.hs b/Annex/Path.hs
index 802ab9c043..6db939e084 100644
--- a/Annex/Path.hs
+++ b/Annex/Path.hs
@@ -65,7 +65,7 @@ programPath = go =<< getEnv "GIT_ANNEX_DIR"
 readProgramFile :: IO (Maybe OsPath)
 readProgramFile = catchDefaultIO Nothing $ do
 	programfile <- programFile
-	fmap toOsPath . headMaybe . lines <$> readFile (fromOsPath programfile)
+	fmap toOsPath . headMaybe . lines <$> readFileString programfile
 
 cannotFindProgram :: IO a
 cannotFindProgram = do
diff --git a/Annex/Sim.hs b/Annex/Sim.hs
index 823d991ad2..fa80b94e22 100644
--- a/Annex/Sim.hs
+++ b/Annex/Sim.hs
@@ -1356,16 +1356,15 @@ suspendSim st = do
 	let st'' = st'
 		{ simRepoState = M.map freeze (simRepoState st')
 		}
-	let statefile = fromOsPath $ 
-		toOsPath (simRootDirectory st'') </> literalOsPath "state"
-	writeFile statefile (show st'')
+	let statefile = toOsPath (simRootDirectory st'') </> literalOsPath "state"
+	writeFileString statefile (show st'')
   where
 	freeze :: SimRepoState SimRepo -> SimRepoState ()
 	freeze rst = rst { simRepo = Nothing }
 
 restoreSim :: OsPath -> IO (Either String (SimState SimRepo))
 restoreSim rootdir = 
-	tryIO (readFile statefile) >>= \case
+	tryIO (readFileString statefile) >>= \case
 		Left err -> return (Left (show err))
 		Right c -> case readMaybe c :: Maybe (SimState ()) of
 			Nothing -> return (Left "unable to parse sim state file")
@@ -1379,7 +1378,7 @@ restoreSim rootdir =
 					}
 				return (Right st'')
   where
-	statefile = fromOsPath $ rootdir </> literalOsPath "state"
+	statefile = rootdir </> literalOsPath "state"
 	thaw st (u, rst) = tryNonAsync (thaw' st u) >>= return . \case
 		Left _ -> (u, rst { simRepo = Nothing })
 		Right r -> (u, rst { simRepo = Just r })
diff --git a/Annex/Ssh.hs b/Annex/Ssh.hs
index a0e4ff9319..2a482dbc3c 100644
--- a/Annex/Ssh.hs
+++ b/Annex/Ssh.hs
@@ -484,4 +484,4 @@ sshAskPassEnv :: String
 sshAskPassEnv = "GIT_ANNEX_SSHASKPASS"
 
 runSshAskPass :: FilePath -> IO ()
-runSshAskPass passfile = putStrLn =<< readFile passfile
+runSshAskPass passfile = putStrLn =<< readFileString (toOsPath passfile)
diff --git a/Annex/YoutubeDl.hs b/Annex/YoutubeDl.hs
index 5b3fbd7158..6c13295955 100644
--- a/Annex/YoutubeDl.hs
+++ b/Annex/YoutubeDl.hs
@@ -94,7 +94,7 @@ youtubeDl' url workdir p uo
 	nofiles = Left $ youtubeDlCommand ++ " did not put any media in its work directory, perhaps it's been configured to store files somewhere else?"
 	toomanyfiles fs = Left $ youtubeDlCommand ++ " downloaded multiple media files; git-annex is only able to deal with one per url: " ++ show fs
 	downloadedfiles = liftIO $ 
-		(nub . lines <$> readFile (fromOsPath filelistfile))
+		(nub . lines <$> readFileString filelistfile)
 			`catchIO` (pure . const [])
 	workdirfiles = liftIO $ filter (/= filelistfile) 
 		<$> (filterM doesFileExist =<< dirContents workdir)
diff --git a/Assistant/DaemonStatus.hs b/Assistant/DaemonStatus.hs
index eeb40605ea..80f18b6996 100644
--- a/Assistant/DaemonStatus.hs
+++ b/Assistant/DaemonStatus.hs
@@ -132,7 +132,7 @@ writeDaemonStatusFile file status =
 		]
 
 readDaemonStatusFile :: FilePath -> IO DaemonStatus
-readDaemonStatusFile file = parse <$> newDaemonStatus <*> readFile file
+readDaemonStatusFile file = parse <$> newDaemonStatus <*> readFileString (toOsPath file)
   where
 	parse status = foldr parseline status . lines
 	parseline line status
diff --git a/Assistant/Install.hs b/Assistant/Install.hs
index 750b4a9adc..c5710ff213 100644
--- a/Assistant/Install.hs
+++ b/Assistant/Install.hs
@@ -57,7 +57,7 @@ ensureInstalled = ifM (isJust <$> getEnv "GIT_ANNEX_PACKAGE_INSTALL")
 		let program = base </> literalOsPath "git-annex"
 		programfile <- programFile
 		createDirectoryIfMissing True (parentDir programfile)
-		writeFile (fromOsPath programfile) (fromOsPath program)
+		writeFileString programfile (fromOsPath program)
 
 #ifdef darwin_HOST_OS
 		autostartfile <- userAutoStart osxAutoStartLabel
@@ -70,7 +70,7 @@ ensureInstalled = ifM (isJust <$> getEnv "GIT_ANNEX_PACKAGE_INSTALL")
 				let bootfile = toOsPath home </> literalOsPath ".termux" </> literalOsPath "boot" </> literalOsPath "git-annex"
 				unlessM (doesFileExist bootfile) $ do
 					createDirectoryIfMissing True (takeDirectory bootfile)
-					writeFile (fromOsPath bootfile) "git-annex assistant --autostart"
+					writeFileString bootfile "git-annex assistant --autostart"
 			, do
 				menufile <- desktopMenuFilePath "git-annex" <$> userDataDir
 				icondir <- iconDir <$> userDataDir
@@ -125,7 +125,7 @@ installFileManagerHooks program = unlessM osAndroid $ do
 	userdata <- userDataDir
 	let kdeServiceMenusdir = userdata </> literalOsPath "kservices5" </> literalOsPath "ServiceMenus"
 	createDirectoryIfMissing True kdeServiceMenusdir
-	writeFile (fromOsPath (kdeServiceMenusdir </> literalOsPath "git-annex.desktop"))
+	writeFileString (kdeServiceMenusdir </> literalOsPath "git-annex.desktop")
 		(kdeDesktopFile actions)
   where
 	genNautilusScript scriptdir action =
@@ -136,7 +136,7 @@ installFileManagerHooks program = unlessM osAndroid $ do
 			]
 	scriptname action = "git-annex " ++ action
 	installscript f c = whenM (safetoinstallscript f) $ do
-		writeFile (fromOsPath f) c
+		writeFileString f c
 		modifyFileMode f $ addModes [ownerExecuteMode]
 	safetoinstallscript f = catchDefaultIO True $
 		elem (encodeBS autoaddedcomment) . fileLines'
diff --git a/Assistant/Install/AutoStart.hs b/Assistant/Install/AutoStart.hs
index 366e202731..c689f9d2fd 100644
--- a/Assistant/Install/AutoStart.hs
+++ b/Assistant/Install/AutoStart.hs
@@ -23,7 +23,7 @@ installAutoStart :: String -> OsPath -> IO ()
 installAutoStart command file = do
 #ifdef darwin_HOST_OS
 	createDirectoryIfMissing True (parentDir file)
-	writeFile (fromOsPath file) $ genOSXAutoStartFile osxAutoStartLabel command
+	writeFileString file $ genOSXAutoStartFile osxAutoStartLabel command
 		["assistant", "--autostart"]
 #else
 	writeDesktopMenuFile (fdoAutostart command) file
diff --git a/Assistant/Restart.hs b/Assistant/Restart.hs
index 658d1ddf18..58a17c12a2 100644
--- a/Assistant/Restart.hs
+++ b/Assistant/Restart.hs
@@ -79,7 +79,7 @@ newAssistantUrl repo = do
 		r <- Git.Config.read =<< Git.Construct.fromPath repo
 		waiturl $ gitAnnexUrlFile r
 	waiturl urlfile = do
-		v <- tryIO $ readFile (fromOsPath urlfile)
+		v <- tryIO $ readFileString urlfile
 		case v of
 			Left _ -> delayed $ waiturl urlfile
 			Right url -> ifM (assistantListening url)
diff --git a/Assistant/Ssh.hs b/Assistant/Ssh.hs
index 420e1efdab..4cbc79ec61 100644
--- a/Assistant/Ssh.hs
+++ b/Assistant/Ssh.hs
@@ -224,8 +224,8 @@ genSshKeyPair = withTmpDir (literalOsPath "git-annex-keygen") $ \dir -> do
 	unless ok $
 		giveup "ssh-keygen failed"
 	SshKeyPair
-		<$> readFile (fromOsPath (dir </> literalOsPath "key.pub"))
-		<*> readFile (fromOsPath (dir </> literalOsPath "key"))
+		<$> readFileString (dir </> literalOsPath "key.pub")
+		<*> readFileString (dir </> literalOsPath "key")
 
 {- Installs a ssh key pair, and sets up ssh config with a mangled hostname
  - that will enable use of the key. This way we avoid changing the user's
@@ -255,7 +255,7 @@ installSshKeyPair sshkeypair sshdata = do
 		writeFileProtected (sshdir </> sshPrivKeyFile sshdata)
 			(sshPrivKey sshkeypair)
 	unlessM (doesFileExist $ sshdir </> sshPubKeyFile sshdata) $
-		writeFile (fromOsPath (sshdir </> sshPubKeyFile sshdata))
+		writeFileString (sshdir </> sshPubKeyFile sshdata)
 			(sshPubKey sshkeypair)
 
 	setSshConfig sshdata
@@ -277,8 +277,10 @@ sshPubKeyFile sshdata = sshPrivKeyFile sshdata <> literalOsPath ".pub"
 setupSshKeyPair :: SshData -> IO (SshData, SshKeyPair)
 setupSshKeyPair sshdata = do
 	sshdir <- sshDir
-	mprivkey <- catchMaybeIO $ readFile (fromOsPath (sshdir </> sshPrivKeyFile sshdata))
-	mpubkey <- catchMaybeIO $ readFile (fromOsPath (sshdir </> sshPubKeyFile sshdata))
+	mprivkey <- catchMaybeIO $ readFileString
+		(sshdir </> sshPrivKeyFile sshdata)
+	mpubkey <- catchMaybeIO $ readFileString
+		(sshdir </> sshPubKeyFile sshdata)
 	keypair <- case (mprivkey, mpubkey) of
 		(Just privkey, Just pubkey) -> return $ SshKeyPair
 			{ sshPubKey = pubkey
@@ -330,15 +332,15 @@ setSshConfig :: SshData -> [(String, String)] -> IO SshData
 setSshConfig sshdata config = do
 	sshdir <- sshDir
 	createDirectoryIfMissing True sshdir
-	let configfile = fromOsPath (sshdir </> literalOsPath "config")
-	unlessM (catchBoolIO $ isInfixOf mangledhost <$> readFile configfile) $ do
-		appendFile configfile $ unlines $
+	let configfile = sshdir </> literalOsPath "config"
+	unlessM (catchBoolIO $ isInfixOf mangledhost <$> readFileString configfile) $ do
+		appendFileString configfile $ unlines $
 			[ ""
 			, "# Added automatically by git-annex"
 			, "Host " ++ mangledhost
 			] ++ map (\(k, v) -> "\t" ++ k ++ " " ++ v)
 				(settings ++ config)
-		setSshConfigMode (toOsPath configfile)
+		setSshConfigMode configfile
 
 	return $ sshdata
 		{ sshHostName = T.pack mangledhost
diff --git a/Assistant/Upgrade.hs b/Assistant/Upgrade.hs
index ca6d5b3ada..1d7c05a5d8 100644
--- a/Assistant/Upgrade.hs
+++ b/Assistant/Upgrade.hs
@@ -160,7 +160,7 @@ upgradeToDistribution newdir cleanup distributionfile = do
 		unlessM (boolSystem (fromOsPath program) [Param "version"]) $
 			giveup "New git-annex program failed to run! Not using."
 		pf <- programFile
-		liftIO $ writeFile (fromOsPath pf) (fromOsPath program)
+		liftIO $ writeFileString pf (fromOsPath program)
 	
 #ifdef darwin_HOST_OS
 	{- OS X uses a dmg, so mount it, and copy the contents into place. -}
@@ -281,7 +281,7 @@ installBase = "git-annex." ++
 deleteFromManifest :: OsPath -> IO ()
 deleteFromManifest dir = do
 	fs <- map (\f -> dir </> toOsPath f) . lines 
-		<$> catchDefaultIO "" (readFile (fromOsPath manifest))
+		<$> catchDefaultIO "" (readFileString manifest)
 	mapM_ (removeWhenExistsWith removeFile) fs
 	removeWhenExistsWith removeFile manifest
 	removeEmptyRecursive dir
diff --git a/Assistant/WebApp/Configurators/Local.hs b/Assistant/WebApp/Configurators/Local.hs
index 0d6b6f1eb3..4574b0fe53 100644
--- a/Assistant/WebApp/Configurators/Local.hs
+++ b/Assistant/WebApp/Configurators/Local.hs
@@ -185,7 +185,7 @@ getAndroidCameraRepositoryR = do
   where
 	addignore = do
 		liftIO $ unlessM (doesFileExist $ literalOsPath ".gitignore") $
-			writeFile ".gitignore" ".thumbnails"
+			writeFileString (literalOsPath ".gitignore") ".thumbnails"
 		void $ inRepo $
 			Git.Command.runBool [Param "add", File ".gitignore"]
 
diff --git a/Assistant/WebApp/Control.hs b/Assistant/WebApp/Control.hs
index 0f0a76584e..a32a05f069 100644
--- a/Assistant/WebApp/Control.hs
+++ b/Assistant/WebApp/Control.hs
@@ -74,5 +74,5 @@ getLogR :: Handler Html
 getLogR = page "Logs" Nothing $ do
 	logfile <- liftAnnex $ fromRepo gitAnnexDaemonLogFile
 	logs <- liftIO $ listLogs (fromOsPath logfile)
-	logcontent <- liftIO $ concat <$> mapM readFile logs
+	logcontent <- liftIO $ concat <$> mapM (readFileString . toOsPath) logs
 	$(widgetFile "control/log")
diff --git a/Assistant/WebApp/Documentation.hs b/Assistant/WebApp/Documentation.hs
index a6dcc03853..bd42945118 100644
--- a/Assistant/WebApp/Documentation.hs
+++ b/Assistant/WebApp/Documentation.hs
@@ -34,7 +34,7 @@ getLicenseR = do
 		Just f -> customPage (Just About) $ do
 			-- no sidebar, just pages of legalese..
 			setTitle "License"
-			license <- liftIO $ readFile (fromOsPath f)
+			license <- liftIO $ readFileString f
 			$(widgetFile "documentation/license")
 
 getRepoGroupR :: Handler Html
diff --git a/Build/Configure.hs b/Build/Configure.hs
index dc5e634016..4b1a0594f9 100644
--- a/Build/Configure.hs
+++ b/Build/Configure.hs
@@ -12,6 +12,7 @@ import Utility.Env.Basic
 import qualified Git.Version
 import Utility.SystemDirectory
 import Utility.OsPath
+import qualified Utility.FileIO as F
 
 import Control.Monad
 import Control.Applicative
@@ -93,7 +94,7 @@ getSshConnectionCaching = Config "sshconnectioncaching" . BoolConfig <$>
 setup :: IO ()
 setup = do
 	createDirectoryIfMissing True (toOsPath tmpDir)
-	writeFile testFile "test file contents"
+	F.writeFileString (toOsPath testFile) "test file contents"
 
 cleanup :: IO ()
 cleanup = removeDirectoryRecursive (toOsPath tmpDir)
diff --git a/Build/DesktopFile.hs b/Build/DesktopFile.hs
index b69fd82854..ad066a8937 100644
--- a/Build/DesktopFile.hs
+++ b/Build/DesktopFile.hs
@@ -74,7 +74,7 @@ install command = do
 		, do
 			programfile <- inDestDir =<< programFile
 			createDirectoryIfMissing True (parentDir programfile)
-			writeFile (fromOsPath programfile) command
+			writeFileString programfile command
 		)
 
 installUser :: FilePath -> IO ()
diff --git a/Build/DistributionUpdate.hs b/Build/DistributionUpdate.hs
index c7566a5a9e..b7223fdfa3 100644
--- a/Build/DistributionUpdate.hs
+++ b/Build/DistributionUpdate.hs
@@ -148,7 +148,7 @@ makeinfos updated changelogversion = do
 					, distributionReleasedate = now
 					, distributionUrgentUpgrade = Just "6.20180626"
 					}
-				liftIO $ writeFile (fromOsPath infofile) $ formatInfoFile d
+				liftIO $ writeFileString infofile $ formatInfoFile d
 				void $ inRepo $ runBool [Param "add", File (fromOsPath infofile)]
 				signFile infofile
 				signFile f
@@ -173,7 +173,7 @@ makeinfos updated changelogversion = do
 	-- Check for out of date info files.
 	infos <- liftIO $ filter (literalOsPath ".info" `OS.isSuffixOf`)
 		<$> emptyWhenDoesNotExist (dirContentsRecursive $ literalOsPath "git-annex")
-	ds <- liftIO $ forM infos (readish <$$> readFile . fromOsPath)
+	ds <- liftIO $ forM infos (readish <$$> readFileString)
 	let dis = zip infos ds
 	let ood = filter outofdate dis
 	return ood
diff --git a/Build/LinuxMkLibs.hs b/Build/LinuxMkLibs.hs
index c081dd83d5..065ac3b1ea 100644
--- a/Build/LinuxMkLibs.hs
+++ b/Build/LinuxMkLibs.hs
@@ -29,6 +29,7 @@ import Utility.FileMode
 import Utility.CopyFile
 import Utility.SystemDirectory
 import qualified Utility.OsString as OS
+import qualified Utility.FileIO as F
 
 mklibs :: OsPath -> a -> IO Bool
 mklibs top _installedbins = do
@@ -47,9 +48,9 @@ mklibs top _installedbins = do
 
 	-- Various files used by runshell to set up env vars used by the
 	-- linker shims.
-	writeFile (fromOsPath (top </> literalOsPath "libdirs"))
+	F.writeFileString (top </> literalOsPath "libdirs")
 		(unlines (map fromOsPath libdirs'))
-	writeFile (fromOsPath (top </> literalOsPath "gconvdir")) $
+	F.writeFileString (top </> literalOsPath "gconvdir") $
 		case gconvlibs of
 			[] -> ""
 			(p:_) -> fromOsPath (parentDir p)
@@ -171,7 +172,7 @@ installLinkerShim top linker exe = do
 	link <- relPathDirToFile (top </> exedir) (top <> linker)
 	unlessM (doesFileExist (top </> exelink)) $
 		createSymbolicLink (fromOsPath link) (fromOsPath (top </> exelink))
-	writeFile (fromOsPath exe) $ unlines
+	F.writeFileString exe $ unlines
 		[ "#!/bin/sh"
 		, "exec \"$GIT_ANNEX_DIR/" ++ fromOsPath exelink ++ "\" --library-path \"$GIT_ANNEX_LD_LIBRARY_PATH\" \"$GIT_ANNEX_DIR/shimmed/" ++ fromOsPath base ++ "/" ++ fromOsPath base ++ "\" \"$@\""
 		]
diff --git a/Build/NullSoftInstaller.hs b/Build/NullSoftInstaller.hs
index 8241ff8dd8..b2e1209878 100644
--- a/Build/NullSoftInstaller.hs
+++ b/Build/NullSoftInstaller.hs
@@ -43,6 +43,7 @@ import Utility.Exception
 import Utility.Directory
 import Utility.SystemDirectory
 import Utility.OsPath
+import qualified Utility.FileIO as F
 import Build.BundledPrograms
 
 main = do
@@ -55,11 +56,11 @@ main = do
 		mustSucceed "sh" [Param "-c", Param $ "zcat standalone/licences.gz > '" ++ license ++ "'"]
 		webappscript <- vbsLauncher tmpdir "git-annex-webapp" "git annex webapp"
 		autostartscript <- vbsLauncher tmpdir "git-annex-autostart" "git annex assistant --autostart"
-		let htmlhelp = fromOsPath $ tmpdir </> literalOsPath "git-annex.html"
-		writeFile htmlhelp htmlHelpText
-		let gitannexcmd = fromOsPath $ tmpdir </> literalOsPath "git-annex.cmd"
-		writeFile gitannexcmd "git annex %*"
-		writeFile nsifile $ makeInstaller
+		let htmlhelp = tmpdir </> literalOsPath "git-annex.html"
+		F.writeFileString htmlhelp htmlHelpText
+		let gitannexcmd = tmpdir </> literalOsPath "git-annex.cmd"
+		F.writeFileString gitannexcmd "git annex %*"
+		F.writeFileString (toOsPath nsifile) $ makeInstaller
 			gitannex gitannexcmd license htmlhelp (winPrograms ++ magicDLLs') magicShare'
 			[ webappscript, autostartscript ]
 		mustSucceed "makensis" [File nsifile]
@@ -85,13 +86,13 @@ main = do
  - box. It expects to be passed the directory where git-annex is installed. -}
 vbsLauncher :: OsPath -> String -> String -> IO String
 vbsLauncher tmpdir basename cmd = do
-	let f = fromOsPath $ tmpdir </> toOsPath (basename ++ ".vbs")
-	writeFile f $ unlines
+	let f = tmpdir </> toOsPath (basename ++ ".vbs")
+	F.writeFileString f $ unlines
 		[ "Set objshell=CreateObject(\"Wscript.Shell\")"
 		, "objShell.CurrentDirectory = Wscript.Arguments.item(0)"
 		, "objShell.Run(\"" ++ cmd ++ "\"), 0, False"
 		]
-	return f
+	return (fromOsPath f)
 
 gitannexprogram :: FilePath
 gitannexprogram = "git-annex.exe"
diff --git a/Build/Standalone.hs b/Build/Standalone.hs
index e0e9e56bee..44e8171707 100644
--- a/Build/Standalone.hs
+++ b/Build/Standalone.hs
@@ -180,19 +180,19 @@ installSkel topdir _basedir = do
 installSkelRest :: OsPath -> OsPath -> Bool -> IO ()
 #ifdef darwin_HOST_OS
 installSkelRest _topdir basedir _hwcaplibs = do
-	plist <- lines <$> readFile "standalone/osx/Info.plist.template"
+	plist <- lines <$> F.readFileString (literalOsPath "standalone/osx/Info.plist.template")
 	version <- getVersion
-	writeFile (fromOsPath (basedir </> literalOsPath "Contents" </> literalOsPath "Info.plist"))
+	F.writeFileString (basedir </> literalOsPath "Contents" </> literalOsPath "Info.plist")
 		(unlines (map (expandversion version) plist))
   where
 	expandversion v l = replace "GIT_ANNEX_VERSION" v l
 #else
 installSkelRest topdir _basedir hwcaplibs = do
-	runshell <- lines <$> readFile "standalone/linux/skel/runshell"
+	runshell <- lines <$> F.readFileString (literalOsPath "standalone/linux/skel/runshell")
 	-- GIT_ANNEX_PACKAGE_INSTALL can be set by a distributor and
 	-- runshell will be modified
 	gapi <- getEnv "GIT_ANNEX_PACKAGE_INSTALL"
-	writeFile (fromOsPath (topdir </> literalOsPath "runshell"))
+	F.writeFileString (topdir </> literalOsPath "runshell")
 		(unlines (map (expandrunshell gapi) runshell))
 	modifyFileMode
 		(topdir </> literalOsPath "runshell")
diff --git a/Build/TestConfig.hs b/Build/TestConfig.hs
index f20972fa8f..c556f7ac25 100644
--- a/Build/TestConfig.hs
+++ b/Build/TestConfig.hs
@@ -1,6 +1,7 @@
 {- Tests the system and generates SysConfig. -}
 
 {-# OPTIONS_GHC -fno-warn-tabs #-}
+{-# LANGUAGE OverloadedStrings #-}
 
 module Build.TestConfig where
 
@@ -9,6 +10,7 @@ import Utility.Monad
 import Utility.SafeCommand
 import Utility.SystemDirectory
 import Utility.OsPath
+import qualified Utility.FileIO as F
 
 import System.IO
 
@@ -42,7 +44,7 @@ instance Show Config where
 		valuetype (MaybeBoolConfig _) = "Maybe Bool"
 
 writeSysConfig :: [Config] -> IO ()
-writeSysConfig config = writeFile "Build/SysConfig" body
+writeSysConfig config = F.writeFileString (literalOsPath "Build/SysConfig") body
   where
 	body = unlines $ header ++ map show config ++ footer
 	header = [
@@ -100,12 +102,16 @@ findCmdPath k command = do
 	ifM (inSearchPath command)
 		( return $ Config k $ MaybeStringConfig $ Just command
 		, do
-			r <- getM find ["/usr/sbin", "/sbin", "/usr/local/sbin"]
+			r <- getM find
+				[ literalOsPath "/usr/sbin"
+				, literalOsPath "/sbin"
+				, literalOsPath "/usr/local/sbin"
+				]
 			return $ Config k $ MaybeStringConfig r
 		)
   where
 	find d =
-		let f = toOsPath d </> toOsPath command
+		let f = d </> toOsPath command
 		in ifM (doesFileExist f)
 			( return (Just (fromOsPath f))
 			, return Nothing
diff --git a/Build/Version.hs b/Build/Version.hs
index 3552814116..762714e89f 100644
--- a/Build/Version.hs
+++ b/Build/Version.hs
@@ -51,7 +51,7 @@ getVersion = do
 	
 getChangelogVersion :: IO Version
 getChangelogVersion = do
-	changelog <- readFile "CHANGELOG"
+	changelog <- F.readFileString (literalOsPath "CHANGELOG")
 	let verline = takeWhile (/= '\n') changelog
 	return $ middle (words verline !! 1)
   where
diff --git a/Command/FuzzTest.hs b/Command/FuzzTest.hs
index 3534e21e63..cd244c6195 100644
--- a/Command/FuzzTest.hs
+++ b/Command/FuzzTest.hs
@@ -178,7 +178,7 @@ runFuzzAction :: FuzzAction -> Annex ()
 runFuzzAction (FuzzAdd (FuzzFile f)) = do
 	createWorkTreeDirectory (parentDir (toOsPath f))
 	n <- liftIO (getStdRandom random :: IO Int)
-	liftIO $ writeFile f $ show n ++ "\n"
+	liftIO $ writeFileString (toOsPath f) $ show n ++ "\n"
 runFuzzAction (FuzzDelete (FuzzFile f)) = liftIO $
 	removeWhenExistsWith removeFile (toOsPath f)
 runFuzzAction (FuzzMove (FuzzFile src) (FuzzFile dest)) = liftIO $
diff --git a/Command/ImportFeed.hs b/Command/ImportFeed.hs
index 613c9dd0f8..7b66a2b507 100644
--- a/Command/ImportFeed.hs
+++ b/Command/ImportFeed.hs
@@ -183,7 +183,7 @@ getFeed o url st =
 					next $ return True
 	
 	debugfeedcontent tmpf msg = do
-		feedcontent <- liftIO $ readFile tmpf
+		feedcontent <- liftIO $ readFileString (toOsPath tmpf)
 		fastDebug "Command.ImportFeed" $ unlines
 			[ "start of feed content"
 			, feedcontent
@@ -611,7 +611,7 @@ checkFeedBroken url = checkFeedBroken' url =<< feedState url
 checkFeedBroken' :: URLString -> OsPath -> Annex Bool
 checkFeedBroken' url f = do
 	prev <- maybe Nothing readish
-		<$> liftIO (catchMaybeIO $ readFile (fromOsPath f))
+		<$> liftIO (catchMaybeIO $ readFileString f)
 	now <- liftIO getCurrentTime
 	case prev of
 		Nothing -> do
diff --git a/Command/Map.hs b/Command/Map.hs
index 7771014504..c83babd4b9 100644
--- a/Command/Map.hs
+++ b/Command/Map.hs
@@ -55,7 +55,7 @@ start = startingNoMessage (ActionItemOther Nothing) $ do
 				<$> fromRepo gitAnnexDir
 				<*> pure (literalOsPath "map.dot")
 
-			liftIO $ writeFile (fromOsPath file) (drawMap rs trustmap umap)
+			liftIO $ writeFileString file (drawMap rs trustmap umap)
 			next $
 				ifM (Annex.getRead Annex.fast)
 					( runViewer file []
diff --git a/Command/Sim.hs b/Command/Sim.hs
index 36357c4398..60e7996e42 100644
--- a/Command/Sim.hs
+++ b/Command/Sim.hs
@@ -70,7 +70,7 @@ startsim' simfile = do
 	let st = emptySimState rng (fromOsPath simdir)
 	case simfile of
 		Nothing -> startup simdir st []
-		Just f -> liftIO (readFile f) >>= \c -> 
+		Just f -> liftIO (readFileString (toOsPath f)) >>= \c -> 
 			case parseSimFile c of
 				Left err -> giveup err
 				Right cs -> startup simdir st cs
diff --git a/Command/Vicfg.hs b/Command/Vicfg.hs
index 4679c598e5..c52b539a24 100644
--- a/Command/Vicfg.hs
+++ b/Command/Vicfg.hs
@@ -49,7 +49,7 @@ start = do
 	createAnnexDirectory $ parentDir f
 	cfg <- getCfg
 	descs <- uuidDescriptions
-	liftIO $ writeFile (fromOsPath f) $ genCfg cfg descs
+	liftIO $ writeFileString f $ genCfg cfg descs
 	vicfg cfg f
 	stop
 
@@ -65,7 +65,7 @@ vicfg curcfg f = do
 	liftIO $ removeWhenExistsWith removeFile f
 	case r of
 		Left s -> do
-			liftIO $ writeFile (fromOsPath f) s
+			liftIO $ writeFileString f s
 			vicfg curcfg f
 		Right newcfg -> setCfg curcfg newcfg
   where
diff --git a/Command/WebApp.hs b/Command/WebApp.hs
index 02e5735d3b..80801c3893 100644
--- a/Command/WebApp.hs
+++ b/Command/WebApp.hs
@@ -90,7 +90,7 @@ start' allowauto o = do
 			( if isJust (listenAddress o) || isJust (listenPort o)
 				then giveup "The assistant is already running, so --listen and --port cannot be used."
 				else do
-					url <- liftIO . readFile . fromOsPath
+					url <- liftIO . readFileString
 						=<< fromRepo gitAnnexUrlFile
 					liftIO $ if isJust listenAddress'
 						then putStrLn url
diff --git a/Config/Files.hs b/Config/Files.hs
index 14450fcc72..7b7c6c49c7 100644
--- a/Config/Files.hs
+++ b/Config/Files.hs
@@ -32,4 +32,4 @@ programFile = userConfigFile (literalOsPath "program")
 noAnnexFileContent :: Maybe OsPath -> IO (Maybe String)
 noAnnexFileContent repoworktree = case repoworktree of
 	Nothing -> return Nothing
-	Just wt -> catchMaybeIO (readFile (fromOsPath (wt </> literalOsPath ".noannex")))
+	Just wt -> catchMaybeIO (readFileString (wt </> literalOsPath ".noannex"))
diff --git a/Config/Files/AutoStart.hs b/Config/Files/AutoStart.hs
index 7307e46d5c..31b6b2edf8 100644
--- a/Config/Files/AutoStart.hs
+++ b/Config/Files/AutoStart.hs
@@ -18,7 +18,7 @@ readAutoStartFile :: IO [OsPath]
 readAutoStartFile = do
 	f <- autoStartFile
 	filter valid . nub . map (dropTrailingPathSeparator . toOsPath) . lines
-		<$> catchDefaultIO "" (readFile (fromOsPath f))
+		<$> catchDefaultIO "" (readFileString f)
   where
 	-- Ignore any relative paths; some old buggy versions added eg "."
 	valid = isAbsolute
@@ -30,7 +30,7 @@ modifyAutoStartFile func = do
 	when (dirs' /= dirs) $ do
 		f <- autoStartFile
 		createDirectoryIfMissing True (parentDir f)
-		viaTmp (writeFile . fromRawFilePath . fromOsPath) f
+		viaTmp writeFileString f
 			(unlines (map fromOsPath dirs'))
 
 {- Adds a directory to the autostart file. If the directory is already
diff --git a/Config/Smudge.hs b/Config/Smudge.hs
index c17eaa1bca..2f38c47725 100644
--- a/Config/Smudge.hs
+++ b/Config/Smudge.hs
@@ -70,7 +70,7 @@ deconfigureSmudgeFilter = do
 	lf <- Annex.fromRepo Git.attributesLocal
 	ls <- liftIO $ catchDefaultIO [] $ 
 		map decodeBS . fileLines' <$> F.readFile' lf
-	liftIO $ writeFile (fromOsPath lf) $ unlines $
+	liftIO $ writeFileString lf $ unlines $
 		filter (\l -> l `notElem` stdattr && not (null l)) ls
 	unsetConfig (ConfigKey "filter.annex.smudge")
 	unsetConfig (ConfigKey "filter.annex.clean")
diff --git a/Database/Keys.hs b/Database/Keys.hs
index d3fce7bbd8..93e659f445 100644
--- a/Database/Keys.hs
+++ b/Database/Keys.hs
@@ -264,7 +264,7 @@ reconcileStaged dbisnew qh = ifM isBareRepo
 	( return mempty
 	, do
 		gitindex <- inRepo currentIndexFile
-		indexcache <- fromOsPath <$> calcRepo' gitAnnexKeysDbIndexCache
+		indexcache <- calcRepo' gitAnnexKeysDbIndexCache
 		withTSDelta (liftIO . genInodeCache gitindex) >>= \case
 			Just cur -> readindexcache indexcache >>= \case
 				Nothing -> go cur indexcache =<< getindextree
@@ -278,7 +278,7 @@ reconcileStaged dbisnew qh = ifM isBareRepo
 	lastindexref = Ref "refs/annex/last-index"
 
 	readindexcache indexcache = liftIO $ maybe Nothing readInodeCache
-		<$> catchMaybeIO (readFile indexcache)
+		<$> catchMaybeIO (readFileString indexcache)
 
 	getoldtree = fromMaybe emptyTree <$> inRepo (Git.Ref.sha lastindexref)
 	
@@ -292,7 +292,7 @@ reconcileStaged dbisnew qh = ifM isBareRepo
 					(Just (fromRef oldtree)) 
 					(fromRef newtree)
 					(procdiff mdfeeder)
-			liftIO $ writeFile indexcache $ showInodeCache cur
+			liftIO $ writeFileString indexcache $ showInodeCache cur
 			-- Storing the tree in a ref makes sure it does not
 			-- get garbage collected, and is available to diff
 			-- against next time.
diff --git a/Git/Construct.hs b/Git/Construct.hs
index afbe4a5232..cd91fd6461 100644
--- a/Git/Construct.hs
+++ b/Git/Construct.hs
@@ -280,7 +280,7 @@ adjustGitDirFile loc = fromMaybe loc <$> adjustGitDirFile' loc
 adjustGitDirFile' :: RepoLocation -> IO (Maybe RepoLocation)
 adjustGitDirFile' loc@(Local {}) = do
 	let gd = gitdir loc
-	c <- firstLine <$> catchDefaultIO "" (readFile (fromOsPath gd))
+	c <- firstLine <$> catchDefaultIO "" (readFileString gd)
 	if gitdirprefix `isPrefixOf` c
 		then do
 			top <- takeDirectory <$> absPath gd
diff --git a/Git/Hook.hs b/Git/Hook.hs
index e5a67bda7d..d1c32fd189 100644
--- a/Git/Hook.hs
+++ b/Git/Hook.hs
@@ -59,7 +59,7 @@ hookWrite h r = ifM (doesFileExist f)
 	f = hookFile h r
 	go = do
 		-- On Windows, using a ByteString as the file content
-		-- avoids the newline translation done by writeFile.
+		-- avoids the newline translation done by writeFileString.
 		-- Hook scripts on Windows could use CRLF endings, but
 		-- they typically use unix newlines, which does work there
 		-- and makes the repository more portable.
@@ -85,11 +85,11 @@ data ExpectedContent = UnexpectedContent | ExpectedContent | OldExpectedContent
 
 expectedContent :: Hook -> Repo -> IO ExpectedContent
 expectedContent h r = do
-	-- Note that on windows, this readFile does newline translation,
+	-- Note that on windows, this readFileString does newline translation,
 	-- and so a hook file that has CRLF will be treated the same as one
 	-- that has LF. That is intentional, since users may have a reason
 	-- to prefer one or the other.
-	content <- readFile $ fromOsPath $ hookFile h r
+	content <- readFileString $ hookFile h r
 	return $ if content == hookScript h
 		then ExpectedContent
 		else if any (content ==) (hookOldScripts h)
diff --git a/Git/Objects.hs b/Git/Objects.hs
index 4d2a2e907b..d39f410074 100644
--- a/Git/Objects.hs
+++ b/Git/Objects.hs
@@ -50,7 +50,7 @@ looseObjectFile r sha = objectsDir r </> toOsPath prefix </> toOsPath rest
 
 listAlternates :: Repo -> IO [FilePath]
 listAlternates r = catchDefaultIO [] $
-	lines <$> readFile (fromOsPath alternatesfile)
+	lines <$> readFileString alternatesfile
   where
 	alternatesfile = objectsDir r </> literalOsPath "info" </> literalOsPath "alternates"
 
diff --git a/Git/Repair.hs b/Git/Repair.hs
index 2f1c31fe71..246b40ed8c 100644
--- a/Git/Repair.hs
+++ b/Git/Repair.hs
@@ -269,7 +269,7 @@ explodePackedRefsFile r = do
 		let dest = gitd </> toOsPath (fromRef' ref)
 		createDirectoryUnder [gitd] (parentDir dest)
 		unlessM (doesFileExist dest) $
-			writeFile (fromOsPath dest) (fromRef sha)
+			writeFileString dest (fromRef sha)
 
 packedRefsFile :: Repo -> OsPath
 packedRefsFile r = localGitDir r </> literalOsPath "packed-refs"
@@ -472,7 +472,7 @@ preRepair :: Repo -> IO ()
 preRepair g = do
 	unlessM (validhead <$> catchDefaultIO "" (decodeBS <$> safeReadFile headfile)) $ do
 		removeWhenExistsWith removeFile headfile
-		writeFile (fromOsPath headfile) "ref: refs/heads/master"
+		writeFileString headfile "ref: refs/heads/master"
 	explodePackedRefsFile g
 	unless (repoIsLocalBare g) $
 		void $ tryIO $ allowWrite $ indexFile g
diff --git a/Logs/File.hs b/Logs/File.hs
index 882dc25369..71a5baeb1c 100644
--- a/Logs/File.hs
+++ b/Logs/File.hs
@@ -38,7 +38,7 @@ writeLogFile :: OsPath -> String -> Annex ()
 writeLogFile f c = createDirWhenNeeded f $ viaTmp writelog f c
   where
 	writelog tmp c' = do
-		liftIO $ writeFile (fromOsPath tmp) c'
+		liftIO $ writeFileString tmp c'
 		setAnnexFilePerm tmp
 
 -- | Runs the action with a handle connected to a temp file.
diff --git a/Logs/FsckResults.hs b/Logs/FsckResults.hs
index b938491092..3234af2493 100644
--- a/Logs/FsckResults.hs
+++ b/Logs/FsckResults.hs
@@ -45,7 +45,7 @@ readFsckResults :: UUID -> Annex FsckResults
 readFsckResults u = do
 	logfile <- fromRepo $ gitAnnexFsckResultsLog u
 	liftIO $ catchDefaultIO (FsckFoundMissing S.empty False) $
-		deserializeFsckResults <$> readFile (fromOsPath logfile)
+		deserializeFsckResults <$> readFileString logfile
 
 deserializeFsckResults :: String -> FsckResults
 deserializeFsckResults = deserialize . lines
diff --git a/Logs/Restage.hs b/Logs/Restage.hs
index 3e3c439598..d63391c814 100644
--- a/Logs/Restage.hs
+++ b/Logs/Restage.hs
@@ -55,7 +55,7 @@ streamRestageLog finalizer processor = do
 			ifM (doesPathExist oldf)
 				( do
 					h <- F.openFile oldf AppendMode
-					hPutStr h =<< readFile (fromOsPath logf)
+					hPutStr h =<< readFileString logf
 					hClose h
 					liftIO $ removeWhenExistsWith removeFile logf
 				, moveFile logf oldf
diff --git a/Logs/Schedule.hs b/Logs/Schedule.hs
index 6727fdd316..7bd839a545 100644
--- a/Logs/Schedule.hs
+++ b/Logs/Schedule.hs
@@ -63,9 +63,9 @@ scheduleChange u a = scheduleSet u . S.toList . a =<< scheduleGet u
 
 getLastRunTimes :: Annex (M.Map ScheduledActivity LocalTime)
 getLastRunTimes = do
-	f <- fromOsPath <$> fromRepo gitAnnexScheduleState
+	f <- fromRepo gitAnnexScheduleState
 	liftIO $ fromMaybe M.empty
-		<$> catchDefaultIO Nothing (readish <$> readFile f)
+		<$> catchDefaultIO Nothing (readish <$> readFileString f)
 
 setLastRunTime :: ScheduledActivity -> LocalTime -> Annex ()
 setLastRunTime activity lastrun = do
diff --git a/Logs/Transfer.hs b/Logs/Transfer.hs
index 85a5f7b824..e0beadab53 100644
--- a/Logs/Transfer.hs
+++ b/Logs/Transfer.hs
@@ -263,7 +263,7 @@ writeTransferInfoFile info tfile = writeLogFile tfile $ writeTransferInfo info
 -- after it's been created with the right perms by writeTransferInfoFile.
 updateTransferInfoFile :: TransferInfo -> OsPath -> IO ()
 updateTransferInfoFile info tfile = 
-	writeFile (fromOsPath tfile) $ writeTransferInfo info
+	writeFileString tfile $ writeTransferInfo info
 
 {- File format is a header line containing the startedTime and any
  - bytesComplete value. Followed by a newline and the associatedFile.
diff --git a/Logs/View.hs b/Logs/View.hs
index 14ee8dcd37..838471f14e 100644
--- a/Logs/View.hs
+++ b/Logs/View.hs
@@ -54,8 +54,8 @@ removeView v = writeViews =<< filter (/= v) <$> recentViews
 
 recentViews :: Annex [View]
 recentViews = do
-	f <- fromOsPath <$> fromRepo gitAnnexViewLog
-	liftIO $ mapMaybe readish . lines <$> catchDefaultIO [] (readFile f)
+	f <- fromRepo gitAnnexViewLog
+	liftIO $ mapMaybe readish . lines <$> catchDefaultIO [] (readFileString f)
 
 {- Gets the currently checked out view, if there is one. 
  -
diff --git a/Remote/Directory/LegacyChunked.hs b/Remote/Directory/LegacyChunked.hs
index 3773ed9172..e32b263b98 100644
--- a/Remote/Directory/LegacyChunked.hs
+++ b/Remote/Directory/LegacyChunked.hs
@@ -33,7 +33,7 @@ withCheckedFiles check d locations k a = go $ locations d k
 		let chunkcount = f ++ Legacy.chunkCount
 		ifM (check chunkcount)
 			( do
-				chunks <- Legacy.listChunks f <$> readFile chunkcount
+				chunks <- Legacy.listChunks f <$> readFileString (toOsPath chunkcount)
 				ifM (allM check chunks)
 					( a chunks , return False )
 			, do
@@ -85,7 +85,7 @@ storeHelper repotop finalizer key storer tmpdir destdir = do
 	recorder f s = do
 		let f' = toOsPath f
 		void $ tryIO $ allowWrite f'
-		writeFile f s
+		writeFileString f' s
 		void $ tryIO $ preventWrite f'
 
 store :: FilePath -> ChunkSize -> (OsPath -> OsPath -> IO ()) -> Key -> L.ByteString -> MeterUpdate -> FilePath -> FilePath -> IO ()
diff --git a/Remote/Tahoe.hs b/Remote/Tahoe.hs
index 2f0cebf188..c58ae362b4 100644
--- a/Remote/Tahoe.hs
+++ b/Remote/Tahoe.hs
@@ -213,7 +213,7 @@ createClient configdir furl = do
 
 writeSharedConvergenceSecret :: TahoeConfigDir -> SharedConvergenceSecret -> IO ()
 writeSharedConvergenceSecret configdir scs = 
-	writeFile (fromOsPath (convergenceFile configdir))
+	writeFileString (convergenceFile configdir)
 		(unlines [scs])
 
 {- The tahoe daemon writes the convergenceFile shortly after it starts
@@ -223,11 +223,11 @@ writeSharedConvergenceSecret configdir scs =
 getSharedConvergenceSecret :: TahoeConfigDir -> IO SharedConvergenceSecret
 getSharedConvergenceSecret configdir = go (60 :: Int)
   where
-	f = fromOsPath $ convergenceFile configdir
+	f = convergenceFile configdir
 	go n
-		| n == 0 = giveup $ "tahoe did not write " ++ f ++ " after 1 minute. Perhaps the daemon failed to start?"
+		| n == 0 = giveup $ "tahoe did not write " ++ fromOsPath f ++ " after 1 minute. Perhaps the daemon failed to start?"
 		| otherwise = do
-			v <- catchMaybeIO (readFile f)
+			v <- catchMaybeIO (readFileString f)
 			case v of
 				Just s | "\n" `isSuffixOf` s || "\r" `isSuffixOf` s ->
 					return $ takeWhile (`notElem` ("\n\r" :: String)) s
diff --git a/Test.hs b/Test.hs
index 62cb88c10f..43a15f8952 100644
--- a/Test.hs
+++ b/Test.hs
@@ -556,8 +556,8 @@ test_magic = intmpclonerepo $ do
 #ifdef WITH_MAGICMIME
 	git "config" ["annex.largefiles", "mimeencoding=binary"]
 		"git config annex.largefiles"
-	writeFile "binary" "\127"
-	writeFile "text" "test\n" 
+	writeFileString (literalOsPath "binary") "\127"
+	writeFileString (literalOsPath "text") "test\n" 
 	git_annex "add" ["binary", "text"]
 		"git-annex add with mimeencoding in largefiles"
 	git_annex "sync" ["--no-content"]
@@ -879,7 +879,7 @@ test_lock = intmpclonerepo $ do
 	changecontent annexedfile
 	git "add" [annexedfile] "add of modified file"
 	runchecks [checkregularfile, checkwritable] annexedfile
-	c <- readFile annexedfile
+	c <- readFileString (toOsPath annexedfile)
 	assertEqual "content of modified file" c (changedcontent annexedfile)
 	git_annex_shouldfail "drop" [annexedfile]
 		"drop with no known copy of modified file should not be allowed"
@@ -921,7 +921,7 @@ test_edit' precommit = intmpclonerepo $ do
 		then git_annex "pre-commit" [] "pre-commit"
 		else git "commit" ["-q", "-m", "contentchanged"] "git commit of edited file"
 	runchecks [checkregularfile, checkwritable] annexedfile
-	c <- readFile annexedfile
+	c <- readFileString (toOsPath annexedfile)
 	assertEqual "content of modified file" c (changedcontent annexedfile)
 	git_annex_shouldfail "drop" [annexedfile] "drop no known copy of modified file should not be allowed"
 
@@ -947,7 +947,7 @@ test_fix = intmpclonerepo $ unlessM (hasUnlockedFiles <$> getTestMode) $ do
 	git "mv" [annexedfile, subdir] "git mv"
 	git_annex "fix" [newfile] "fix of moved file"
 	runchecks [checklink, checkunwritable] newfile
-	c <- readFile newfile
+	c <- readFileString (toOsPath newfile)
 	assertEqual "content of moved file" c (content annexedfile)
   where
 	subdir = "s"
@@ -1069,7 +1069,8 @@ test_migrate' usegitattributes = intmpclonerepo $ do
 	annexed_present sha1annexedfile
 	if usegitattributes
 		then do
-			writeFile ".gitattributes" "* annex.backend=SHA1"
+			writeFileString (literalOsPath ".gitattributes")
+				"* annex.backend=SHA1"
 			git_annex "migrate" [sha1annexedfile]
 				"migrate sha1annexedfile"
 			git_annex "migrate" [annexedfile]
@@ -1085,7 +1086,8 @@ test_migrate' usegitattributes = intmpclonerepo $ do
 	checkbackend sha1annexedfile backendSHA1
 
 	-- check that reversing a migration works
-	writeFile ".gitattributes" "* annex.backend=SHA256"
+	writeFileString (literalOsPath ".gitattributes")
+		"* annex.backend=SHA256"
 	git_annex "migrate" [sha1annexedfile] "migrate sha1annexedfile"
 	git_annex "migrate" [annexedfile] "migrate annexedfile"
 	annexed_present annexedfile
@@ -1531,7 +1533,7 @@ test_nonannexed_file_conflict_resolution = do
 		length v == 1
 			@? (what ++ " too many variant files in: " ++ show v)
 		conflictor `elem` l @? (what ++ " conflictor file missing in: " ++ show l)
-		s <- catchMaybeIO $ readFile $ fromOsPath $
+		s <- catchMaybeIO $ readFileString $
 			toOsPath d </> toOsPath conflictor
 		s == Just nonannexed_content
 			@? (what ++ " wrong content for nonannexed file: " ++ show s)
@@ -2074,9 +2076,9 @@ test_export_import = intmpclonerepo $ do
 	dircontains "import" (content "newimport3")
   where
 	dircontains f v = do
-		let df = fromOsPath (literalOsPath "dir" </> stringToOsPath f)
-		((v==) <$> readFile df)
-			@? ("did not find expected content of " ++ df)
+		let df = literalOsPath "dir" </> stringToOsPath f
+		((v==) <$> readFileString df)
+			@? ("did not find expected content of " ++ fromOsPath df)
 	writedir f = writecontent (fromOsPath (literalOsPath "dir" </> stringToOsPath f))
 	-- When on an adjusted branch, this updates the master branch
 	-- to match it, which is necessary since the master branch is going
@@ -2111,9 +2113,9 @@ test_export_import_subdir = intmpclonerepo $ do
 	testexport
   where
 	dircontains f v = do
-		let df = fromOsPath (literalOsPath "dir" </> toOsPath f)
-		((v==) <$> readFile df)
-			@? ("did not find expected content of " ++ df)
+		let df = literalOsPath "dir" </> toOsPath f
+		((v==) <$> readFileString df)
+			@? ("did not find expected content of " ++ fromOsPath df)
 	
 	subdir = "subdir"
 	subannexedfile = fromOsPath $
diff --git a/Test/Framework.hs b/Test/Framework.hs
index 3d0a96fa2f..fee78b4875 100644
--- a/Test/Framework.hs
+++ b/Test/Framework.hs
@@ -391,7 +391,7 @@ checkexists f =
 
 checkcontent :: FilePath -> Assertion
 checkcontent f = do
-	c <- Utility.Exception.catchDefaultIO "could not read file" $ readFile f
+	c <- Utility.Exception.catchDefaultIO "could not read file" $ readFileString (toOsPath f)
 	assertEqual ("checkcontent " ++ f) (content f) c
 
 checkunwritable :: FilePath -> Assertion
@@ -415,7 +415,7 @@ checkdangling :: FilePath -> Assertion
 checkdangling f = ifM (annexeval Config.crippledFileSystem)
 	( return () -- probably no real symlinks to test
 	, do
-		r <- tryIO $ readFile f
+		r <- tryIO $ readFileString (toOsPath f)
 		case r of
 			Left _ -> return () -- expected; dangling link
 			Right _ -> assertFailure $ f ++ " was not a dangling link as expected"
@@ -675,9 +675,10 @@ writecontent :: FilePath -> String -> IO ()
 writecontent f c = go (10000000 :: Integer)
   where
 	go ticsleft = do
-		oldmtime <- catchMaybeIO $ getModificationTime (toOsPath f)
-		writeFile f c
-		newmtime <- getModificationTime (toOsPath f)
+		let f' = toOsPath f
+		oldmtime <- catchMaybeIO $ getModificationTime f'
+		writeFileString f' c
+		newmtime <- getModificationTime f'
 		if Just newmtime == oldmtime
 			then do
 				threadDelay 100000
diff --git a/Upgrade/V2.hs b/Upgrade/V2.hs
index bd01cb5ab0..215179cc9a 100644
--- a/Upgrade/V2.hs
+++ b/Upgrade/V2.hs
@@ -87,7 +87,7 @@ locationLogs = do
 inject :: OsPath -> OsPath -> Annex ()
 inject source dest = do
 	old <- fromRepo olddir
-	new <- liftIO (readFile $ fromOsPath $ old </> source)
+	new <- liftIO $ readFileString (old </> source)
 	Annex.Branch.change (Annex.Branch.RegardingUUID []) dest $ \prev -> 
 		encodeBL $ unlines $ nub $ lines (decodeBL prev) ++ lines new
 
@@ -141,7 +141,7 @@ gitAttributesUnWrite repo = do
 	whenM (doesFileExist attributes) $ do
 		c <- map decodeBS . fileLines'
 			<$> F.readFile' attributes
-		liftIO $ viaTmp (writeFile . fromOsPath) attributes 
+		liftIO $ viaTmp writeFileString attributes 
 			(unlines $ filter (`notElem` attrLines) c)
 		Git.Command.run [Param "add", File (fromOsPath attributes)] repo
 
diff --git a/Upgrade/V7.hs b/Upgrade/V7.hs
index caabe13d2f..218096f208 100644
--- a/Upgrade/V7.hs
+++ b/Upgrade/V7.hs
@@ -136,7 +136,7 @@ updateSmudgeFilter = do
 		<$> catchDefaultIO "" (F.readFile' lf)
 	let ls' = removedotfilter ls
 	when (ls /= ls') $
-		liftIO $ writeFile (fromOsPath lf) (unlines ls')
+		liftIO $ writeFileString lf (unlines ls')
   where
 	removedotfilter ("* filter=annex":".* !filter":rest) =
 		"* filter=annex" : removedotfilter rest
diff --git a/Utility/Daemon.hs b/Utility/Daemon.hs
index a95503f0d2..bd654da7dd 100644
--- a/Utility/Daemon.hs
+++ b/Utility/Daemon.hs
@@ -121,9 +121,9 @@ lockPidFile pidfile = do
 	unlessM (isNothing <$> checkDaemon pidfile)
 		alreadyRunning
 	pid <- getPID
-	writeFile (fromOsPath pidfile) (show pid)
+	writeFileString pidfile (show pid)
 	lckfile <- winLockFile pid pidfile
-	writeFile (fromOsPath lckfile) ""
+	writeFileString lckfile ""
 	void $ lockExclusive lckfile
 #endif
 
@@ -147,7 +147,7 @@ checkDaemon pidfile = bracket setup cleanup go
 	cleanup Nothing = return ()
 	go (Just fd) = catchDefaultIO Nothing $ do
 		locked <- getLock fd (ReadLock, AbsoluteSeek, 0, 0)
-		p <- readish <$> readFile (fromOsPath pidfile)
+		p <- readish <$> readFileString pidfile
 		return (check locked p)
 	go Nothing = return Nothing
 
@@ -161,7 +161,7 @@ checkDaemon pidfile = bracket setup cleanup go
 			"; expected " ++ show pid ++ " )"
 #else
 checkDaemon pidfile = maybe (return Nothing) (check . readish)
-	=<< catchMaybeIO (readFile (fromOsPath pidfile))
+	=<< catchMaybeIO (readFileString pidfile)
   where
 	check Nothing = return Nothing
 	check (Just pid) = do
diff --git a/Utility/FileMode.hs b/Utility/FileMode.hs
index a4d5cc5a20..8c7de891ea 100644
--- a/Utility/FileMode.hs
+++ b/Utility/FileMode.hs
@@ -171,7 +171,7 @@ setSticky f = modifyFileMode f $ addModes [stickyMode]
  - When possible, this is done using the umask.
  -
  - On a filesystem that does not support file permissions, this is the same
- - as writeFile.
+ - as writeFileString.
  -}
 writeFileProtected :: OsPath -> String -> IO ()
 writeFileProtected file content = writeFileProtected' file 
diff --git a/Utility/FreeDesktop.hs b/Utility/FreeDesktop.hs
index 71ec3a3c7b..8fe6cbf9dc 100644
--- a/Utility/FreeDesktop.hs
+++ b/Utility/FreeDesktop.hs
@@ -75,7 +75,7 @@ buildDesktopMenuFile d = unlines ("[Desktop Entry]" : map keyvalue d) ++ "\n"
 writeDesktopMenuFile :: DesktopEntry -> OsPath -> IO ()
 writeDesktopMenuFile d file = do
 	createDirectoryIfMissing True (takeDirectory file)
-	writeFile (fromOsPath file) $ buildDesktopMenuFile d
+	writeFileString file $ buildDesktopMenuFile d
 
 {- Path to use for a desktop menu file, in either the systemDataDir or
  - the userDataDir -}
diff --git a/Utility/InodeCache.hs b/Utility/InodeCache.hs
index 7e1b18aa35..08c4a6c8a6 100644
--- a/Utility/InodeCache.hs
+++ b/Utility/InodeCache.hs
@@ -234,7 +234,7 @@ noTSDelta = TSDelta (pure 0)
 writeSentinalFile :: SentinalFile -> IO ()
 writeSentinalFile s = do
 	F.writeFile' (sentinalFile s) mempty
-	maybe noop (writeFile (fromOsPath (sentinalCacheFile s)) . showInodeCache)
+	maybe noop (writeFileString (sentinalCacheFile s) . showInodeCache)
 		=<< genInodeCache (sentinalFile s) noTSDelta
 
 data SentinalStatus = SentinalStatus
@@ -263,7 +263,7 @@ checkSentinalFile s = do
 				Just new -> return $ calc old new
   where
 	loadoldcache = catchDefaultIO Nothing $
-		readInodeCache <$> readFile (fromOsPath (sentinalCacheFile s))
+		readInodeCache <$> readFileString (sentinalCacheFile s)
 	gennewcache = genInodeCache (sentinalFile s) noTSDelta
 	calc (InodeCache (InodeCachePrim oldinode oldsize oldmtime)) (InodeCache (InodeCachePrim newinode newsize newmtime)) =
 		SentinalStatus (not unchanged) tsdelta
diff --git a/Utility/LockFile/PidLock.hs b/Utility/LockFile/PidLock.hs
index 2c480a354d..67cf78d62e 100644
--- a/Utility/LockFile/PidLock.hs
+++ b/Utility/LockFile/PidLock.hs
@@ -41,6 +41,7 @@ import Utility.Env.Set
 import Utility.Tmp
 import Utility.RawFilePath
 import Utility.OsPath
+import qualified Utility.FileIO as F
 import qualified Utility.LockFile.Posix as Posix
 
 import System.IO
@@ -77,7 +78,7 @@ mkPidLock = PidLock
 
 readPidLock :: PidLockFile -> IO (Maybe PidLock)
 readPidLock lockfile = (readish =<<)
-	<$> catchMaybeIO (readFile (fromOsPath lockfile))
+	<$> catchMaybeIO (F.readFileString lockfile)
 
 -- To avoid races when taking over a stale pid lock, a side lock is used.
 -- This is a regular posix exclusive lock.
@@ -214,7 +215,7 @@ linkToLock (Just _) src dest = do
 					(CloseOnExecFlag True)
 				fdToHandle fd
 			let cleanup = hClose
-			let go h = readFile (fromOsPath src) >>= hPutStr h
+			let go h = F.readFileString src >>= hPutStr h
 			bracket setup cleanup go
 			getFileStatus dest'
   where
diff --git a/Utility/Misc.hs b/Utility/Misc.hs
index ac98873ab1..c81ca21f28 100644
--- a/Utility/Misc.hs
+++ b/Utility/Misc.hs
@@ -110,7 +110,7 @@ fileLines' = map stripCR . S8.lines
 fileLines' = S8.lines
 #endif
 
--- One windows, writeFile does NewlineMode translation,
+-- On windows, writeFile does NewlineMode translation,
 -- adding CR before LF. When converting to ByteString, use this to emulate that.
 linesFile :: L.ByteString -> L.ByteString
 #ifndef mingw32_HOST_OS
diff --git a/Utility/Shell.hs b/Utility/Shell.hs
index 0d43994f98..5f9b08909d 100644
--- a/Utility/Shell.hs
+++ b/Utility/Shell.hs
@@ -37,7 +37,7 @@ findShellCommand f = do
 #ifndef mingw32_HOST_OS
 	defcmd
 #else
-	l <- catchDefaultIO Nothing $ headMaybe . lines <$> readFile (fromOsPath f)
+	l <- catchDefaultIO Nothing $ headMaybe . lines <$> readFileString f
 	case l of
 		Just ('#':'!':rest) -> case words rest of
 			[] -> defcmd
diff --git a/Utility/Tmp.hs b/Utility/Tmp.hs
index c47cdfcb0b..582f6849fc 100644
--- a/Utility/Tmp.hs
+++ b/Utility/Tmp.hs
@@ -49,13 +49,13 @@ openTmpFileIn dir template = F.openTempFile dir template
 		let loc = ioeGetLocation e ++ " template " ++ decodeBS (fromOsPath template)
 		in annotateIOError e loc Nothing Nothing
 
-{- Runs an action like writeFile, writing to a temp file first and
+{- Runs an action like writeFileString, writing to a temp file first and
  - then moving it into place. The temp file is stored in the same
  - directory as the final file to avoid cross-device renames.
  -
  - While this uses a temp file, the file will end up with the same
- - mode as it would when using writeFile, unless the writer action changes
- - it.
+ - mode as it would when using writeFileString, unless the writer action
+ - changes it.
  -}
 viaTmp :: (MonadMask m, MonadIO m) => (OsPath -> v -> m ()) -> OsPath -> v -> m ()
 viaTmp a file content = bracketIO setup cleanup use
diff --git a/Utility/Tor.hs b/Utility/Tor.hs
index a49d7375a7..05ece394fe 100644
--- a/Utility/Tor.hs
+++ b/Utility/Tor.hs
@@ -71,7 +71,7 @@ connectHiddenService (OnionAddress address) port = do
 addHiddenService :: AppName -> UserID -> UniqueIdent -> IO (OnionAddress, OnionPort)
 addHiddenService appname uid ident = do
 	prepHiddenServiceSocketDir appname uid ident
-	ls <- lines <$> (readFile . fromOsPath =<< findTorrc)
+	ls <- lines <$> (readFileString =<< findTorrc)
 	let portssocks = mapMaybe (parseportsock . separate isSpace) ls
 	case filter (\(_, s) -> s == fromOsPath sockfile) portssocks of
 		((p, _s):_) -> waithiddenservice 1 p
@@ -80,7 +80,7 @@ addHiddenService appname uid ident = do
 			let newport = fromMaybe (error "internal") $ headMaybe $
 				filter (`notElem` map fst portssocks) highports
 			torrc <- findTorrc
-			writeFile (fromOsPath torrc) $ unlines $
+			writeFileString torrc $ unlines $
 				ls ++
 				[ ""
 				, "HiddenServiceDir " ++ fromOsPath (hiddenServiceDir appname uid ident)
@@ -112,7 +112,7 @@ addHiddenService appname uid ident = do
 	waithiddenservice :: Int -> OnionPort -> IO (OnionAddress, OnionPort)
 	waithiddenservice 0 _ = giveup "tor failed to create hidden service, perhaps the tor service is not running"
 	waithiddenservice n p = do
-		v <- tryIO $ readFile $ fromOsPath $
+		v <- tryIO $ readFileString $
 			hiddenServiceHostnameFile appname uid ident
 		case v of
 			Right s | ".onion\n" `isSuffixOf` s ->
@@ -152,7 +152,7 @@ hiddenServiceSocketFile appname uid ident =
 getHiddenServiceSocketFile :: AppName -> UserID -> UniqueIdent -> IO (Maybe OsPath)
 getHiddenServiceSocketFile _appname uid ident = 
 	parse . map words . lines <$> catchDefaultIO "" 
-		(readFile . fromOsPath =<< findTorrc)
+		(readFileString =<< findTorrc)
   where
 	parse [] = Nothing
 	parse (("HiddenServiceDir":hsdir:[]):("HiddenServicePort":_hsport:hsaddr:[]):rest)