Rototil the way disklabel -r reads and writes labels.

In particular the 'read' part plays 'hunt the disklabel' in order to get a
label into a local buffer - from where it can be displayed/edited.
The 'write' part makes a separate scan of the disk looking for places to
write the label.
The main changes are:
- It can no longer write the first 8k of the mbr to the pbr (or v.v.)
- All labels on the disk (that it can find) get updated during a write
- With -A all the labels are displayed (inc. those deleted by -D)
- Addition of -D which will delete (by one's complimenting dk_magic{2}) and
  existing labels before writing labels to the expected locations.
- -v gives some verbose output to stderr, -vv more etc
A better basis for processing incorrect endian labels, or labels from other
architectures.

sbin/disklabel/Makefile

@@ -1,4 +1,4 @@
-#	$NetBSD: Makefile,v 1.57 2005/06/23 00:54:47 fvdl Exp $
+#	$NetBSD: Makefile,v 1.58 2005/10/19 21:22:21 dsl Exp $
 #	@(#)Makefile	8.2 (Berkeley) 3/17/94
 
 PROG=	disklabel
@@ -15,11 +15,6 @@ LDADD+= -lutil
 CPPFLAGS+= -DSTRICT_CYLINDER_ALIGNMENT
 .endif
 
-.if (${MACHINE} == "alpha") || (${MACHINE} == "x68k") || (${MACHINE} == "hp700")
-# preserve the non-disklabel portions of the first 8KB of the disk
-CPPFLAGS+= -DSAVEBOOTAREA
-.endif
-
 .if ( 0 \
 	|| ${MACHINE} == "acorn26" \
 	|| ${MACHINE} == "acorn32" \
@@ -40,8 +35,6 @@ CPPFLAGS+= -DSAVEBOOTAREA
     )
 # use MBR partition info
 CPPFLAGS+= -DUSE_MBR
-# preserve the non-disklabel portions of the first 8KB of the disk
-CPPFLAGS+= -DSAVEBOOTAREA
 # recognize old MBR partition ID for a while
 CPPFLAGS+= -DCOMPAT_386BSD_MBRPART
 .endif

sbin/disklabel/extern.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: extern.h,v 1.8 2001/12/13 13:52:13 reinoud Exp $	*/
+/*	$NetBSD: extern.h,v 1.9 2005/10/19 21:22:21 dsl Exp $	*/
 
 /*
  * Copyright (c) 1997 Christos Zoulas.  All rights reserved.
@@ -29,13 +29,12 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-int	writelabel(int, char *, struct disklabel *);
+int	writelabel(int, struct disklabel *);
 int	checklabel(struct disklabel *);
 void	showinfo(FILE *, struct disklabel *, const char *);
 void	showpartitions(FILE *, struct disklabel *, int);
 void	showpartition(FILE *, struct disklabel *, int, int);
 void	interact(struct disklabel *, int);
 
-extern	char	 bootarea[];
-extern	char	*specname;
+extern	char	specname[];
 extern	int	 Cflag;

sbin/disklabel/interact.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: interact.c,v 1.26 2005/06/27 01:00:05 christos Exp $	*/
+/*	$NetBSD: interact.c,v 1.27 2005/10/19 21:22:21 dsl Exp $	*/
 
 /*
  * Copyright (c) 1997 Christos Zoulas.  All rights reserved.
@@ -35,7 +35,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: interact.c,v 1.26 2005/06/27 01:00:05 christos Exp $");
+__RCSID("$NetBSD: interact.c,v 1.27 2005/10/19 21:22:21 dsl Exp $");
 #endif /* lint */
 
 #include <sys/param.h>
@@ -571,7 +571,7 @@ cmd_label(struct disklabel *lp, char *s, int fd)
 		return;
 	}
 
-	if (writelabel(fd, bootarea, lp) != 0) {
+	if (writelabel(fd, lp) != 0) {
 		printf("Label not written\n");
 		return;
 	}