Corrected implication that /boot/boot0 comes from MBR.

Added detail about fdisk and /boot/mbr to head off reader assumption
that FreeBSD's boot manager is FreeBSD-fdisk's default boot manager.

Added detail to statement about 512 byte boot program
to head off debatable claims that it's untrue, and also
to inform the reader.

Approved by:    keramida

en_US.ISO8859-1/books/handbook/boot/chapter.sgml

@@ -128,14 +128,20 @@
       <title>MBR, <filename>/boot/boot0</filename></title>
       <indexterm><primary>Master Boot Record (MBR)</primary></indexterm>
 
-      <para>The FreeBSD MBR is located in <filename>/boot/boot0</filename>.
-	This is a <emphasis>copy</emphasis> of the MBR, as the real MBR must
-	be placed on a special part of the disk, outside the FreeBSD
-	area.</para>
+      <para>The MBR installed by FreeBSD's installer and by boot0cfg(8)
+        are based on <filename>/boot/boot0</filename>.  The MBR is the first
+        sector of a disk, outside slices.  (The MBR installed by fdisk(8),
+        by default, is based on <filename>/boot/mbr</filename>; it is
+        similar to the PC-DOS MBR and it boots the slice marked
+        <emphasis>active</emphasis> without prompting the user as the
+        FreeBSD MBR does.)
 
       <para><filename>boot0</filename> is very simple, since the
 	program in the <abbrev>MBR</abbrev> can only be 512 bytes in
-	size.  If you have installed the FreeBSD MBR and have installed
+	size.
+        (Actually, it can only be 446 bytes because of the slice
+        table and the 0x55AA identifier at the end of the MBR).
+               If you have installed the FreeBSD MBR and have installed
 	multiple operating systems on your hard disks then you will see a
 	display similar to this one at boot time:</para>