diff --git a/grive/src/Config.cc b/grive/src/Config.cc
index a740a5d..b5fbbef 100644
--- a/grive/src/Config.cc
+++ b/grive/src/Config.cc
@@ -56,10 +56,6 @@ Json Config::Read( const std::string& filename )
 	}
 	catch ( Exception& e )
 	{
-// 		throw Error()
-// 			<< File( filename )
-// 			<< expt::ErrMsg("Cannot open config file ")
-// 			<< expt::Nested(e) ;
 		return Json() ;
 	}
 }
diff --git a/libgrive/src/util/OS.cc b/libgrive/src/util/OS.cc
index 77077ab..31cc959 100644
--- a/libgrive/src/util/OS.cc
+++ b/libgrive/src/util/OS.cc
@@ -73,7 +73,12 @@ void SetFileTime( const std::string& filename, const DateTime& t )
 {
 	struct timeval tvp[2] = { t.Tv(), t.Tv() } ;
 	if ( ::utimes( filename.c_str(), tvp ) != 0 )
-		throw expt::ErrMsg( "cannot set file time" ) ;
+		BOOST_THROW_EXCEPTION(
+			Error()
+				<< boost::errinfo_api_function("utimes")
+				<< boost::errinfo_errno(errno)
+				<< boost::errinfo_file_name(filename)
+		) ;
 }
 
 } } // end of namespaces
diff --git a/libgrive/src/util/StdioFile.cc b/libgrive/src/util/StdioFile.cc
index adca10e..a15bb91 100644
--- a/libgrive/src/util/StdioFile.cc
+++ b/libgrive/src/util/StdioFile.cc
@@ -30,6 +30,8 @@
 #include <boost/exception/errinfo_file_open_mode.hpp>
 #include <boost/exception/info.hpp>
 
+#include <sys/stat.h>
+
 namespace gr {
 
 StdioFile::StdioFile( const std::string& filename, const char *mode ) : m_file( 0 )
@@ -110,4 +112,28 @@ long StdioFile::Tell() const
 	return std::ftell( m_file ) ;
 }
 
+void StdioFile::Chmod( int mode )
+{
+	assert( m_file != 0 ) ;
+	
+	int fd = ::fileno(m_file) ;
+	if ( fd == -1 )
+	{
+		BOOST_THROW_EXCEPTION(
+			Error()
+				<< boost::errinfo_api_function("fileno")
+				<< boost::errinfo_errno(errno)
+		) ;
+	}
+	
+	if ( ::fchmod( fd, mode ) != 0 )
+	{
+		BOOST_THROW_EXCEPTION(
+			Error()
+				<< boost::errinfo_api_function("fchmod")
+				<< boost::errinfo_errno(errno)
+		) ;
+	}
+}
+
 } // end of namespace
diff --git a/libgrive/src/util/StdioFile.hh b/libgrive/src/util/StdioFile.hh
index d6ea1d2..002fd53 100644
--- a/libgrive/src/util/StdioFile.hh
+++ b/libgrive/src/util/StdioFile.hh
@@ -48,6 +48,8 @@ public :
 	int Seek( long offset, int whence ) ;
 	long Tell() const ;
 	
+	void Chmod( int mode ) ;
+	
 private :
 	std::FILE	*m_file ;
 } ;