diff --git a/lib/libdisk/Makefile b/lib/libdisk/Makefile
index e4396f542af9..6a5fcdbd7f4c 100644
--- a/lib/libdisk/Makefile
+++ b/lib/libdisk/Makefile
@@ -1,6 +1,6 @@
 .PATH:	/usr/src/sbin/disklabel
 OBJS=	tst01.o blocks.o disklabel.o dkcksum.o chunk.o disk.o change.o \
-	create_chunk.o
+	create_chunk.o rules.o
 CFLAGS+= -Wall
 
 test:	tst01
diff --git a/lib/libdisk/change.c b/lib/libdisk/change.c
index 17dd7827984e..b1db61c34a21 100644
--- a/lib/libdisk/change.c
+++ b/lib/libdisk/change.c
@@ -17,7 +17,6 @@
 #include <string.h>
 #include <err.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
 struct disk *
diff --git a/lib/libdisk/chunk.c b/lib/libdisk/chunk.c
index 088b5ab2b12a..a286cb11d7f6 100644
--- a/lib/libdisk/chunk.c
+++ b/lib/libdisk/chunk.c
@@ -15,11 +15,11 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include <err.h>
 #include "libdisk.h"
 
 CHAR_N;
+
 #define new_chunk() malloc(sizeof(struct chunk))
 
 /* Is c2 completely inside c1 ? */
@@ -206,6 +206,10 @@ Add_Chunk(struct disk *d, u_long offset, u_long size, char *name, chunk_e type,
 		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
 	if(!c1 && type == part)
 		c1 = Find_Mother_Chunk(d->chunks,offset,end,freebsd);
+	if(!c1 && type == reserved)
+		c1 = Find_Mother_Chunk(d->chunks,offset,end,extended);
+	if(!c1 && type == reserved)
+		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
 	if(!c1)
 		return __LINE__;
 	for(c2=c1->part;c2;c2=c2->next) {
@@ -252,26 +256,25 @@ Bios_Limit_Chunk(struct chunk *c1, u_long limit)
 }
 
 int
-Delete_Chunk(struct disk *d, u_long offset, u_long end, chunk_e type)
+Delete_Chunk(struct disk *d, struct chunk *c)
 {
 	struct chunk *c1=0,*c2,*c3;
+	chunk_e type = c->type;
 
 	if(type == whole) 
 		return 1;
 	if(!c1 && (type == freebsd || type == fat || type == foo))
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,extended);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,extended);
 	if(!c1 && (type == freebsd || type == fat || type == foo))
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,whole);
 	if(!c1 && type == extended)
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,whole);
 	if(!c1 && type == part)
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,freebsd);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,freebsd);
 	if(!c1)
 		return 1;
 	for(c2=c1->part;c2;c2=c2->next) {
-		if (c2->offset == offset &&
-		    c2->end == end &&
-		    c2->type == type) {
+		if (c2 == c) {
 			c2->type = unused;
 			c2->subtype = 0;
 			c2->flags = 0;
@@ -329,7 +332,7 @@ Collapse_Chunk(struct disk *d, struct chunk *c1)
 		return 0;
 
 	if(c3->type == unused && c3->size == c1->size) {
-		Delete_Chunk(d,c1->offset, c1->end, c1->type);
+		Delete_Chunk(d,c1);
 		return 1;
 	}
 	if(c3->type == unused) {
diff --git a/lib/libdisk/create_chunk.c b/lib/libdisk/create_chunk.c
index 6664820b80b4..7abcac9a0e2d 100644
--- a/lib/libdisk/create_chunk.c
+++ b/lib/libdisk/create_chunk.c
@@ -15,7 +15,6 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include <err.h>
 #include "libdisk.h"
 
diff --git a/lib/libdisk/disk.c b/lib/libdisk/disk.c
index 5ff2a217a25d..4f78c5ae46e2 100644
--- a/lib/libdisk/disk.c
+++ b/lib/libdisk/disk.c
@@ -20,7 +20,6 @@
 #include <sys/ioctl.h>
 #include <sys/disklabel.h>
 #include <sys/diskslice.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
 #define DOSPTYP_EXTENDED        5
@@ -66,6 +65,7 @@ Int_Open_Disk(char *name, u_long size)
 		size = ds.dss_slices[WHOLE_DISK_SLICE].ds_size;
 
 	Add_Chunk(d, 0, size, name,whole,0,0);
+	Add_Chunk(d, 0, 1, "-",reserved,0,0);
 	
 	for(i=2;i<ds.dss_nslices;i++) {
 		char sname[20];
@@ -94,6 +94,9 @@ Int_Open_Disk(char *name, u_long size)
 		flags |= CHUNK_ALIGN;
 		Add_Chunk(d,ds.dss_slices[i].ds_offset,
 			ds.dss_slices[i].ds_size, sname,ce,subtype,flags);
+		if (ce == extended)
+			Add_Chunk(d,ds.dss_slices[i].ds_offset,
+				1, "-",reserved, subtype, flags);
 		if (ds.dss_slices[i].ds_type == 0xa5) {
 			struct disklabel *dl;
 			int j;
diff --git a/lib/libdisk/libdisk.h b/lib/libdisk/libdisk.h
index 04c5a2f95418..2946f90fb0b3 100644
--- a/lib/libdisk/libdisk.h
+++ b/lib/libdisk/libdisk.h
@@ -1,13 +1,25 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
+ * ----------------------------------------------------------------------------
+ *
+ * $Id$
+ *
+ */
 
 typedef enum {whole, foo, fat, freebsd, extended, part, unused, reserved} chunk_e;
+
 #define CHAR_N static char *chunk_n[] = { \
 	"whole","foo","fat","freebsd","extended","part","unused","reserved"};
 
 struct disk {
 	char		*name;
 	u_long		flags;
-#define DISK_ON_TRACK	1
-#define DISK_REAL_GEOM	2
+#		define DISK_ON_TRACK	1
+#		define DISK_REAL_GEOM	2
 	u_long		real_cyl;
 	u_long		real_hd;
 	u_long		real_sect;
@@ -26,36 +38,79 @@ struct chunk {
 	char		*name;
 	chunk_e		type;
 	int		subtype;
-#define SUBTYPE_BSD_FS          1
-#define SUBTYPE_BSD_SWAP        2
-#define SUBTYPE_BSD_UNUSED      3
+#		define SUBTYPE_BSD_FS          1
+#		define SUBTYPE_BSD_SWAP        2
+#		define SUBTYPE_BSD_UNUSED      3
 	u_long		flags;
-#define CHUNK_PAST_1024		1
-	/* this chunk cannot be booted from */
-#define CHUNK_BSD_COMPAT	2
-	/* this chunk is in the BSD-compatibility, and has a short name
-         * too, ie wd0s4f -> wd0f
-         */ 
-#define CHUNK_BAD144		4
-	/* this chunk has bad144 mapping */
-#define CHUNK_ALIGN		8
+#		define CHUNK_PAST_1024		1
+			/* this chunk cannot be booted from */
+#		define CHUNK_BSD_COMPAT	2
+			/* this chunk is in the BSD-compatibility, and has a 
+			 * short name too, ie wd0s4f -> wd0f
+         		*/ 
+#		define CHUNK_BAD144		4
+			/* this chunk has bad144 mapping */
+#		define CHUNK_ALIGN		8
 };
 
-struct disk *Open_Disk(char *devname);
-void Free_Disk(struct disk *disk);
-void Debug_Disk(struct disk *disk);
-struct disk *Clone_Disk(struct disk *disk);
+struct disk *
+Open_Disk(char *devname);
+	/* Will open the named disk, and return populated tree.
+	 */	
 
-struct disk *Set_Phys_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
-void Set_Bios_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+struct disk *
+Clone_Disk(struct disk *disk);
+	/* Clone a copy of a tree.  Useful for "Undo" functionality
+	 */
 
-int Delete_Chunk(struct disk *disk, u_long offset, u_long end, chunk_e type);
-void Collapse_Disk(struct disk *disk);
-int Collapse_Chunk(struct disk *disk, struct chunk *chunk);
+void 
+Free_Disk(struct disk *disk);
+	/* Free a tree made with Open_Disk() or Clone_Disk()
+	 */
 
-int Create_Chunk(struct disk *disk, u_long offset, u_long size, chunk_e type, int subtype, u_long flags);
+void
+Debug_Disk(struct disk *disk);
+	/* Print the content of the tree to stdout
+	 */
 
-/* Implementation details */
+struct disk *
+Set_Phys_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+	/* Use a different physical geometry.  Makes sense for ST506 disks only.
+	 * The tree returned is read from the disk, using this geometry.
+	 */
+
+void 
+Set_Bios_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+	/* Set the geometry the bios uses.
+	 */
+
+int 
+Delete_Chunk(struct disk *disk, struct chunk *);
+	/* Free a chunk of disk_space 
+	 */
+
+void
+Collapse_Disk(struct disk *disk);
+	/* Experimental, do not use.
+	 */
+int
+Collapse_Chunk(struct disk *disk, struct chunk *chunk);
+	/* Experimental, do not use.
+	 */
+
+int 
+Create_Chunk(struct disk *disk, u_long offset, u_long size, chunk_e type, int subtype, u_long flags);
+	/* Create a chunk with the specified paramters
+	 */
+
+char * 
+CheckRules(struct disk *);
+	/* Return char* to warnings about broken design rules in this disklayout
+	 */
+
+/* 
+ * Implementation details  >>> DO NOT USE <<<
+ */
 
 struct disk *Int_Open_Disk(char *devname, u_long maxsize);
 
diff --git a/lib/libdisk/rules.c b/lib/libdisk/rules.c
new file mode 100644
index 000000000000..7db89ea9e52b
--- /dev/null
+++ b/lib/libdisk/rules.c
@@ -0,0 +1,95 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
+ * ----------------------------------------------------------------------------
+ *
+ * $Id$
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/diskslice.h>
+#include <sys/disklabel.h>
+#include <err.h>
+#include "libdisk.h"
+
+/*
+ *  Rule#0:
+ *	Chunks of type 'whole' can have max NDOSPART children.
+ */
+void
+Rule_000(struct disk *d, struct chunk *c, char *msg)
+{
+	int i;
+	struct chunk *c1;
+
+	if (c->type != whole)
+		return;
+	for (i=0, c1=c->part; c1; c1=c1->next)
+		if (c1->type != unused)
+			i++;
+	if (i <= NDOSPART)
+		return;
+	sprintf(msg+strlen(msg),
+		"%d is too many children of the 'whole' chunk.  Max is %d\n",
+		i, NDOSPART);
+}
+
+/* 
+ * Rule#1:
+ *	All children of 'whole' must be track-aligned
+ */
+void
+Rule_001(struct disk *d, struct chunk *c, char *msg)
+{
+	int i;
+	struct chunk *c1;
+
+	if (c->type != whole)
+		return;
+	for (i=0, c1=c->part; c1; c1=c1->next) {
+		if (c1->type == reserved)
+			continue;
+		if (c1->type == unused)
+			continue;
+		if (!Aligned(d,c1->offset))
+			sprintf(msg+strlen(msg),
+		    "chunk '%s' [%ld..%ld] does not start on a track boundary\n",
+				c1->name,c1->offset,c1->end);
+		if (!Aligned(d,c1->end+1))
+			sprintf(msg+strlen(msg),
+		    "chunk '%s' [%ld..%ld] does not end on a track boundary\n",
+				c1->name,c1->offset,c1->end);
+	}
+}
+
+void
+Check_Chunk(struct disk *d, struct chunk *c, char *msg)
+{
+	Rule_000(d,c,msg);
+	Rule_001(d,c,msg);
+	if (c->part)
+		Check_Chunk(d,c->part,msg);
+	if (c->next)
+		Check_Chunk(d,c->next,msg);
+	return;
+}
+
+char *
+CheckRules(struct disk *d)
+{
+	char msg[BUFSIZ];
+
+	*msg = '\0';
+	Check_Chunk(d,d->chunks,msg);
+	if (*msg)
+		return strdup(msg);
+	return 0;
+}
diff --git a/lib/libdisk/tst01.c b/lib/libdisk/tst01.c
index bcc13448cf66..9320356584c0 100644
--- a/lib/libdisk/tst01.c
+++ b/lib/libdisk/tst01.c
@@ -14,37 +14,8 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/types.h>
-#include <sys/ioctl.h>
-#include <sys/disklabel.h>
-#include <sys/diskslice.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
-void
-fprint_diskslices(FILE *fi, struct diskslices *ds)
-{
-	int i;
-
-	printf("@%p: struct diskslices\n",ds);
-	printf("\tdss_first_bsd_slice = %d\n",ds->dss_first_bsd_slice);
-	printf("\tdss_nslices = %d\n",ds->dss_nslices);
-	for(i=0;i<ds->dss_nslices;i++) {
-		printf("\tdss_slices[%d] = struct diskslice",i);
-		if (i == 0)
-			printf(" /* FreeBSD compatibility slice */\n");
-		else if (i == 1)
-			printf(" /* Whole disk slice */\n");
-		else if (i < 6)
-			printf(" /* Primary MBR slice %d */\n",i-1);
-		else
-			printf("\n");
-		printf("\t\tds_offset = %lu\n",ds->dss_slices[i].ds_offset);
-		printf("\t\tds_size = %lu\n",ds->dss_slices[i].ds_size);
-		printf("\t\tds_type = %u\n",ds->dss_slices[i].ds_type);
-		printf("\t\tds_openmask = %u\n",ds->dss_slices[i].ds_openmask);
-	}
-}
-
 int
 main(int argc, char **argv)
 {
@@ -55,12 +26,12 @@ main(int argc, char **argv)
 		d = Open_Disk(argv[i]);
 		if (!d) continue;
 		Debug_Disk(d);
-		Delete_Chunk(d,0,4108599,freebsd);
-		Debug_Disk(d);
-		printf("Create=%d\n",Create_Chunk(d,0,32768,fat,0,0));
-		printf("Create=%d\n",Create_Chunk(d,192512,409600,freebsd,0,0));
-		printf("Create=%d\n",Create_Chunk(d,192512,409600,part,0,0));
+		if (d->chunks->size == 1411200)
+			Set_Bios_Geom(d,1024,15,63);
+		else
+			Set_Bios_Geom(d,2003,64,32);
 		Debug_Disk(d);
+		printf("<%s>\n",CheckRules(d));
 	}
 	exit (0);
 }
diff --git a/release/libdisk/Makefile b/release/libdisk/Makefile
index e4396f542af9..6a5fcdbd7f4c 100644
--- a/release/libdisk/Makefile
+++ b/release/libdisk/Makefile
@@ -1,6 +1,6 @@
 .PATH:	/usr/src/sbin/disklabel
 OBJS=	tst01.o blocks.o disklabel.o dkcksum.o chunk.o disk.o change.o \
-	create_chunk.o
+	create_chunk.o rules.o
 CFLAGS+= -Wall
 
 test:	tst01
diff --git a/release/libdisk/change.c b/release/libdisk/change.c
index 17dd7827984e..b1db61c34a21 100644
--- a/release/libdisk/change.c
+++ b/release/libdisk/change.c
@@ -17,7 +17,6 @@
 #include <string.h>
 #include <err.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
 struct disk *
diff --git a/release/libdisk/chunk.c b/release/libdisk/chunk.c
index 088b5ab2b12a..a286cb11d7f6 100644
--- a/release/libdisk/chunk.c
+++ b/release/libdisk/chunk.c
@@ -15,11 +15,11 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include <err.h>
 #include "libdisk.h"
 
 CHAR_N;
+
 #define new_chunk() malloc(sizeof(struct chunk))
 
 /* Is c2 completely inside c1 ? */
@@ -206,6 +206,10 @@ Add_Chunk(struct disk *d, u_long offset, u_long size, char *name, chunk_e type,
 		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
 	if(!c1 && type == part)
 		c1 = Find_Mother_Chunk(d->chunks,offset,end,freebsd);
+	if(!c1 && type == reserved)
+		c1 = Find_Mother_Chunk(d->chunks,offset,end,extended);
+	if(!c1 && type == reserved)
+		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
 	if(!c1)
 		return __LINE__;
 	for(c2=c1->part;c2;c2=c2->next) {
@@ -252,26 +256,25 @@ Bios_Limit_Chunk(struct chunk *c1, u_long limit)
 }
 
 int
-Delete_Chunk(struct disk *d, u_long offset, u_long end, chunk_e type)
+Delete_Chunk(struct disk *d, struct chunk *c)
 {
 	struct chunk *c1=0,*c2,*c3;
+	chunk_e type = c->type;
 
 	if(type == whole) 
 		return 1;
 	if(!c1 && (type == freebsd || type == fat || type == foo))
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,extended);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,extended);
 	if(!c1 && (type == freebsd || type == fat || type == foo))
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,whole);
 	if(!c1 && type == extended)
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,whole);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,whole);
 	if(!c1 && type == part)
-		c1 = Find_Mother_Chunk(d->chunks,offset,end,freebsd);
+		c1 = Find_Mother_Chunk(d->chunks,c->offset,c->end,freebsd);
 	if(!c1)
 		return 1;
 	for(c2=c1->part;c2;c2=c2->next) {
-		if (c2->offset == offset &&
-		    c2->end == end &&
-		    c2->type == type) {
+		if (c2 == c) {
 			c2->type = unused;
 			c2->subtype = 0;
 			c2->flags = 0;
@@ -329,7 +332,7 @@ Collapse_Chunk(struct disk *d, struct chunk *c1)
 		return 0;
 
 	if(c3->type == unused && c3->size == c1->size) {
-		Delete_Chunk(d,c1->offset, c1->end, c1->type);
+		Delete_Chunk(d,c1);
 		return 1;
 	}
 	if(c3->type == unused) {
diff --git a/release/libdisk/create_chunk.c b/release/libdisk/create_chunk.c
index 6664820b80b4..7abcac9a0e2d 100644
--- a/release/libdisk/create_chunk.c
+++ b/release/libdisk/create_chunk.c
@@ -15,7 +15,6 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/types.h>
-#include <sys/queue.h>
 #include <err.h>
 #include "libdisk.h"
 
diff --git a/release/libdisk/disk.c b/release/libdisk/disk.c
index 5ff2a217a25d..4f78c5ae46e2 100644
--- a/release/libdisk/disk.c
+++ b/release/libdisk/disk.c
@@ -20,7 +20,6 @@
 #include <sys/ioctl.h>
 #include <sys/disklabel.h>
 #include <sys/diskslice.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
 #define DOSPTYP_EXTENDED        5
@@ -66,6 +65,7 @@ Int_Open_Disk(char *name, u_long size)
 		size = ds.dss_slices[WHOLE_DISK_SLICE].ds_size;
 
 	Add_Chunk(d, 0, size, name,whole,0,0);
+	Add_Chunk(d, 0, 1, "-",reserved,0,0);
 	
 	for(i=2;i<ds.dss_nslices;i++) {
 		char sname[20];
@@ -94,6 +94,9 @@ Int_Open_Disk(char *name, u_long size)
 		flags |= CHUNK_ALIGN;
 		Add_Chunk(d,ds.dss_slices[i].ds_offset,
 			ds.dss_slices[i].ds_size, sname,ce,subtype,flags);
+		if (ce == extended)
+			Add_Chunk(d,ds.dss_slices[i].ds_offset,
+				1, "-",reserved, subtype, flags);
 		if (ds.dss_slices[i].ds_type == 0xa5) {
 			struct disklabel *dl;
 			int j;
diff --git a/release/libdisk/libdisk.h b/release/libdisk/libdisk.h
index 04c5a2f95418..2946f90fb0b3 100644
--- a/release/libdisk/libdisk.h
+++ b/release/libdisk/libdisk.h
@@ -1,13 +1,25 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
+ * ----------------------------------------------------------------------------
+ *
+ * $Id$
+ *
+ */
 
 typedef enum {whole, foo, fat, freebsd, extended, part, unused, reserved} chunk_e;
+
 #define CHAR_N static char *chunk_n[] = { \
 	"whole","foo","fat","freebsd","extended","part","unused","reserved"};
 
 struct disk {
 	char		*name;
 	u_long		flags;
-#define DISK_ON_TRACK	1
-#define DISK_REAL_GEOM	2
+#		define DISK_ON_TRACK	1
+#		define DISK_REAL_GEOM	2
 	u_long		real_cyl;
 	u_long		real_hd;
 	u_long		real_sect;
@@ -26,36 +38,79 @@ struct chunk {
 	char		*name;
 	chunk_e		type;
 	int		subtype;
-#define SUBTYPE_BSD_FS          1
-#define SUBTYPE_BSD_SWAP        2
-#define SUBTYPE_BSD_UNUSED      3
+#		define SUBTYPE_BSD_FS          1
+#		define SUBTYPE_BSD_SWAP        2
+#		define SUBTYPE_BSD_UNUSED      3
 	u_long		flags;
-#define CHUNK_PAST_1024		1
-	/* this chunk cannot be booted from */
-#define CHUNK_BSD_COMPAT	2
-	/* this chunk is in the BSD-compatibility, and has a short name
-         * too, ie wd0s4f -> wd0f
-         */ 
-#define CHUNK_BAD144		4
-	/* this chunk has bad144 mapping */
-#define CHUNK_ALIGN		8
+#		define CHUNK_PAST_1024		1
+			/* this chunk cannot be booted from */
+#		define CHUNK_BSD_COMPAT	2
+			/* this chunk is in the BSD-compatibility, and has a 
+			 * short name too, ie wd0s4f -> wd0f
+         		*/ 
+#		define CHUNK_BAD144		4
+			/* this chunk has bad144 mapping */
+#		define CHUNK_ALIGN		8
 };
 
-struct disk *Open_Disk(char *devname);
-void Free_Disk(struct disk *disk);
-void Debug_Disk(struct disk *disk);
-struct disk *Clone_Disk(struct disk *disk);
+struct disk *
+Open_Disk(char *devname);
+	/* Will open the named disk, and return populated tree.
+	 */	
 
-struct disk *Set_Phys_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
-void Set_Bios_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+struct disk *
+Clone_Disk(struct disk *disk);
+	/* Clone a copy of a tree.  Useful for "Undo" functionality
+	 */
 
-int Delete_Chunk(struct disk *disk, u_long offset, u_long end, chunk_e type);
-void Collapse_Disk(struct disk *disk);
-int Collapse_Chunk(struct disk *disk, struct chunk *chunk);
+void 
+Free_Disk(struct disk *disk);
+	/* Free a tree made with Open_Disk() or Clone_Disk()
+	 */
 
-int Create_Chunk(struct disk *disk, u_long offset, u_long size, chunk_e type, int subtype, u_long flags);
+void
+Debug_Disk(struct disk *disk);
+	/* Print the content of the tree to stdout
+	 */
 
-/* Implementation details */
+struct disk *
+Set_Phys_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+	/* Use a different physical geometry.  Makes sense for ST506 disks only.
+	 * The tree returned is read from the disk, using this geometry.
+	 */
+
+void 
+Set_Bios_Geom(struct disk *disk, u_long cyl, u_long heads, u_long sects);
+	/* Set the geometry the bios uses.
+	 */
+
+int 
+Delete_Chunk(struct disk *disk, struct chunk *);
+	/* Free a chunk of disk_space 
+	 */
+
+void
+Collapse_Disk(struct disk *disk);
+	/* Experimental, do not use.
+	 */
+int
+Collapse_Chunk(struct disk *disk, struct chunk *chunk);
+	/* Experimental, do not use.
+	 */
+
+int 
+Create_Chunk(struct disk *disk, u_long offset, u_long size, chunk_e type, int subtype, u_long flags);
+	/* Create a chunk with the specified paramters
+	 */
+
+char * 
+CheckRules(struct disk *);
+	/* Return char* to warnings about broken design rules in this disklayout
+	 */
+
+/* 
+ * Implementation details  >>> DO NOT USE <<<
+ */
 
 struct disk *Int_Open_Disk(char *devname, u_long maxsize);
 
diff --git a/release/libdisk/rules.c b/release/libdisk/rules.c
new file mode 100644
index 000000000000..7db89ea9e52b
--- /dev/null
+++ b/release/libdisk/rules.c
@@ -0,0 +1,95 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
+ * ----------------------------------------------------------------------------
+ *
+ * $Id$
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/diskslice.h>
+#include <sys/disklabel.h>
+#include <err.h>
+#include "libdisk.h"
+
+/*
+ *  Rule#0:
+ *	Chunks of type 'whole' can have max NDOSPART children.
+ */
+void
+Rule_000(struct disk *d, struct chunk *c, char *msg)
+{
+	int i;
+	struct chunk *c1;
+
+	if (c->type != whole)
+		return;
+	for (i=0, c1=c->part; c1; c1=c1->next)
+		if (c1->type != unused)
+			i++;
+	if (i <= NDOSPART)
+		return;
+	sprintf(msg+strlen(msg),
+		"%d is too many children of the 'whole' chunk.  Max is %d\n",
+		i, NDOSPART);
+}
+
+/* 
+ * Rule#1:
+ *	All children of 'whole' must be track-aligned
+ */
+void
+Rule_001(struct disk *d, struct chunk *c, char *msg)
+{
+	int i;
+	struct chunk *c1;
+
+	if (c->type != whole)
+		return;
+	for (i=0, c1=c->part; c1; c1=c1->next) {
+		if (c1->type == reserved)
+			continue;
+		if (c1->type == unused)
+			continue;
+		if (!Aligned(d,c1->offset))
+			sprintf(msg+strlen(msg),
+		    "chunk '%s' [%ld..%ld] does not start on a track boundary\n",
+				c1->name,c1->offset,c1->end);
+		if (!Aligned(d,c1->end+1))
+			sprintf(msg+strlen(msg),
+		    "chunk '%s' [%ld..%ld] does not end on a track boundary\n",
+				c1->name,c1->offset,c1->end);
+	}
+}
+
+void
+Check_Chunk(struct disk *d, struct chunk *c, char *msg)
+{
+	Rule_000(d,c,msg);
+	Rule_001(d,c,msg);
+	if (c->part)
+		Check_Chunk(d,c->part,msg);
+	if (c->next)
+		Check_Chunk(d,c->next,msg);
+	return;
+}
+
+char *
+CheckRules(struct disk *d)
+{
+	char msg[BUFSIZ];
+
+	*msg = '\0';
+	Check_Chunk(d,d->chunks,msg);
+	if (*msg)
+		return strdup(msg);
+	return 0;
+}
diff --git a/release/libdisk/tst01.c b/release/libdisk/tst01.c
index bcc13448cf66..9320356584c0 100644
--- a/release/libdisk/tst01.c
+++ b/release/libdisk/tst01.c
@@ -14,37 +14,8 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/types.h>
-#include <sys/ioctl.h>
-#include <sys/disklabel.h>
-#include <sys/diskslice.h>
-#include <sys/queue.h>
 #include "libdisk.h"
 
-void
-fprint_diskslices(FILE *fi, struct diskslices *ds)
-{
-	int i;
-
-	printf("@%p: struct diskslices\n",ds);
-	printf("\tdss_first_bsd_slice = %d\n",ds->dss_first_bsd_slice);
-	printf("\tdss_nslices = %d\n",ds->dss_nslices);
-	for(i=0;i<ds->dss_nslices;i++) {
-		printf("\tdss_slices[%d] = struct diskslice",i);
-		if (i == 0)
-			printf(" /* FreeBSD compatibility slice */\n");
-		else if (i == 1)
-			printf(" /* Whole disk slice */\n");
-		else if (i < 6)
-			printf(" /* Primary MBR slice %d */\n",i-1);
-		else
-			printf("\n");
-		printf("\t\tds_offset = %lu\n",ds->dss_slices[i].ds_offset);
-		printf("\t\tds_size = %lu\n",ds->dss_slices[i].ds_size);
-		printf("\t\tds_type = %u\n",ds->dss_slices[i].ds_type);
-		printf("\t\tds_openmask = %u\n",ds->dss_slices[i].ds_openmask);
-	}
-}
-
 int
 main(int argc, char **argv)
 {
@@ -55,12 +26,12 @@ main(int argc, char **argv)
 		d = Open_Disk(argv[i]);
 		if (!d) continue;
 		Debug_Disk(d);
-		Delete_Chunk(d,0,4108599,freebsd);
-		Debug_Disk(d);
-		printf("Create=%d\n",Create_Chunk(d,0,32768,fat,0,0));
-		printf("Create=%d\n",Create_Chunk(d,192512,409600,freebsd,0,0));
-		printf("Create=%d\n",Create_Chunk(d,192512,409600,part,0,0));
+		if (d->chunks->size == 1411200)
+			Set_Bios_Geom(d,1024,15,63);
+		else
+			Set_Bios_Geom(d,2003,64,32);
 		Debug_Disk(d);
+		printf("<%s>\n",CheckRules(d));
 	}
 	exit (0);
 }