diff --git a/usr.sbin/boot0cfg/boot0cfg.8 b/usr.sbin/boot0cfg/boot0cfg.8
index bb73d753d058..bdeb482a847f 100644
--- a/usr.sbin/boot0cfg/boot0cfg.8
+++ b/usr.sbin/boot0cfg/boot0cfg.8
@@ -22,7 +22,7 @@
 .\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 .\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\"	$Id: boot0cfg.8,v 1.2 1999/02/22 09:36:54 rnordier Exp $
+.\"	$Id: boot0cfg.8,v 1.3 1999/02/26 14:57:17 rnordier Exp $
 .\"
 .Dd February 21, 1999
 .Dt BOOT0CFG 8
@@ -36,6 +36,7 @@
 .Op Fl b Ar boot0
 .Op Fl d Ar drive
 .Op Fl f Ar file
+.Op Fl m Ar mask
 .Op Fl o Ar options
 .Op Fl t Ar ticks
 .Ar disk
@@ -89,6 +90,11 @@ is acceptable here.
 Specify that a backup copy of the preexisting MBR should be written to
 .Ar file .
 This file is created if it does not exist, and truncated if it does.
+.It Fl m Ar mask
+Specify slices to be enabled/disabled, where
+.Ar mask
+is an integer between 0 (no slices enabled) and 0xf (all four slices
+enabled).
 .It Fl o Ar options
 A comma-separated string of any of the following options may be
 specified (with
diff --git a/usr.sbin/boot0cfg/boot0cfg.c b/usr.sbin/boot0cfg/boot0cfg.c
index 20fdcc34e90c..0d9ac017d5c9 100644
--- a/usr.sbin/boot0cfg/boot0cfg.c
+++ b/usr.sbin/boot0cfg/boot0cfg.c
@@ -26,7 +26,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-	"$Id: boot0cfg.c,v 1.2 1999/02/22 09:36:54 rnordier Exp $";
+	"$Id: boot0cfg.c,v 1.3 1999/02/26 14:57:17 rnordier Exp $";
 #endif /* not lint */
 
 #include <sys/param.h>
@@ -85,17 +85,17 @@ main(int argc, char *argv[])
     const char *bpath, *fpath, *disk;
     ssize_t n;
     int B_flag, v_flag, o_flag;
-    int d_arg, t_arg;
+    int d_arg, m_arg, t_arg;
     int o_and, o_or;
     int fd, fd1, up, c, i;
 
     bpath = "/boot/boot0";
     fpath = NULL;
     B_flag = v_flag = o_flag = 0;
-    d_arg = t_arg = -1;
+    d_arg = m_arg = t_arg = -1;
     o_and = 0xff;
     o_or = 0;
-    while ((c = getopt(argc, argv, "Bvb:d:f:o:t:")) != -1)
+    while ((c = getopt(argc, argv, "Bvb:d:f:m:o:t:")) != -1)
         switch (c) {
         case 'B':
             B_flag = 1;
@@ -112,6 +112,9 @@ main(int argc, char *argv[])
         case 'f':
             fpath = optarg;
             break;
+        case 'm':
+            m_arg = argtoi(optarg, 0, 0xf, 'm');
+            break;
         case 'o':
             stropt(optarg, &o_and, &o_or);
             o_flag = 1;
@@ -157,6 +160,10 @@ main(int argc, char *argv[])
     }
     if (d_arg != -1)
 	buf[OFF_DRIVE] = d_arg;
+    if (m_arg != -1) {
+	buf[OFF_FLAGS] &= 0xf0;
+	buf[OFF_FLAGS] |= m_arg;
+    }
     if (o_flag) {
         buf[OFF_FLAGS] &= o_and;
         buf[OFF_FLAGS] |= o_or;
@@ -188,7 +195,8 @@ main(int argc, char *argv[])
                        part[i].dp_size);
             }
         printf("\n");
-        printf("drive=0x%x  options=", buf[OFF_DRIVE]);
+        printf("drive=0x%x  mask=0x%x  options=", buf[OFF_DRIVE],
+	       buf[OFF_FLAGS] & 0xf);
         for (i = 0; i < nopt; i++) {
             if (i)
                 printf(",");
@@ -264,7 +272,7 @@ static void
 usage(void)
 {
     fprintf(stderr, "%s\n%s\n",
-    "usage: boot0cfg [-Bv] [-b boot0] [-d drive] [-f file] [-o options]",
-    "                [-t ticks] disk");
+    "usage: boot0cfg [-Bv] [-b boot0] [-d drive] [-f file] [-m mask]",
+    "                [-o options] [-t ticks] disk");
     exit(1);
 }