Heya Simon. I've noticed that in ghc 6.4.2, ghc-pkg doesn't create the file (or maybe just the directory) when trying to register a package: rm -r ~/.ghc/i386-linux-6.4.2 /usr/bin/ghc-pkg update .installed-pkg-config --user ghc-pkg.bin: /home/ijones/.ghc/i386-linux-6.4.2/package.conf: getPermissions: does not exist (No such file or directory) Cabal could try to create the file & directory w/ something like what you have in ghc-pkg plus createDirectoryIfMissing, but I'm a bit nervous of using the System.Info stuff since I know it's pretty new. I'd like to keep cabal working w/ ghc 6.2. We can probably solve this by creating a ghc 6.3 version of Distribution.GHCPackageConfig.maybeCreateLocalPackageConfig and calling it around line 149 of Distribution.Simple.Register. Here's how ghc-pkg generates the filename: appdir <- getAppUserDataDirectory "ghc" let subdir = targetARCH ++ '-':targetOS ++ '-':version archdir = appdir `joinFileName` subdir user_conf = archdir `joinFileName` "package.conf" user_exists <- doesFileExist user_conf I'm not sure where the bug is in ghc-pkg; it's not obvious to me, but it'll probably be obvious to you. Should we implement a cabal workaround? Has anyone complained about this? peace, isaac