diff --git a/em_multistrap b/em_multistrap
index f7e5378..3830cf5 100755
--- a/em_multistrap
+++ b/em_multistrap
@@ -40,6 +40,9 @@ while( @ARGV ) {
 	elsif (/^(-f|--file)$/) {
 		$file = shift(@ARGV);
 	}
+	elsif (/^(-a|--arch)$/) {
+		$arch = shift(@ARGV);
+	}
 	else {
 		die "$progname: Unknown option $_.\n";
 	}
@@ -63,7 +66,7 @@ foreach $section (sort keys %keys)
 {
 	if ($section eq "general")
 	{
-		$arch = $keys{$section}{'arch'};
+		$arch = $keys{$section}{'arch'} if (not defined $arch);
 		$retries = $keys{$section}{'retries'};
 		$dir = $keys{$section}{'directory'};
 		$forceunpack = lc($keys{$section}{'forceunpack'});
@@ -234,11 +237,15 @@ sub usageversion {
 $progname version $ourversion
 
 Usage:
- $progname -f CONFIG_FILE
+ $progname [-a ARCH] [-d DIR] -f CONFIG_FILE
  $progname -?|-h|--help|--version
 
-Options:
+Command:
  -f|--file CONFIG_FILE:  path the the multistrap configuration file.
+
+Options:
+ -a|--arch ARCHITECTURE: override the configuration file architecture.
+ -d|--dir PATH:          override the configuration file directory.
  -?|-h|--help:           print this usage message and exit
  --version:              print this usage message and exit
 
@@ -248,6 +255,17 @@ debootstrap options, architecture, extra packages and the mirror to use
 for each repository.
 
 Example configuration:
+[General]
+arch=arm
+directory=/opt/multistrap/
+retries=5
+# extract all downloaded archives as well as those
+# unpacked by debootstrap.
+forceunpack=false
+# the order of sections is important.
+# debootstraps are unpacked in this sequence.
+debootstrap=Debian
+
 [Debian]
 packages=
 source=http://ftp.uk.debian.org/debian
@@ -256,7 +274,9 @@ script=
 options=
 
 This will result in a completely normal debootstrap of Debian lenny from
-the specified mirror.
+the specified mirror, for ARM in /opt/multistrap/.
+
+'Architecture' and 'directory' can be overridden on the command line.
 
 Specify a package to extend the debootstap to include that package and
 all dependencies.
@@ -292,6 +312,10 @@ END
 
 =pod
 
+=head1 Name
+
+em_multistrap - extends debootstrap for multiple repository support
+
 =head1 Description
 
 em_multistrap extends debootstrap to provide support for multiple
@@ -355,4 +379,8 @@ As with debootstrap, em_multistrap will continue after errors although
 you may want to purge $directory/var/cache/apt/archives from time to
 time.
 
+em_multistrap does not currently implement machine:variant support
+but the build directory is not packed up at the end of the run so
+other scripts can be used to implement customisations.
+
 =cut