Try to preserve the fdisk table in the primary bootstrap, should it

already exist.

Mention the cases where this doesn't work in the BUGS section of the
man page.

1 files changed, 20 insertions, 0 deletions

diff --git a/sbin/disklabel/disklabel.8 b/sbin/disklabel/disklabel.8
index 1cc33abe7aff..ce1b1689fb37 100644
--- a/sbin/disklabel/disklabel.8
+++ b/sbin/disklabel/disklabel.8
@@ -362,3 +362,23 @@ will not install bootstrap code that overlaps it.
 When a disk name is given without a full pathname,
 the constructed device name uses the ``a'' partition on the tahoe,
 the ``c'' partition on all others.
+.Pp
+For the i386 architecture, the primary bootstrap sector contains
+an embedded
+.Em fdisk
+table.
+.Nm Disklabel
+takes care to not clobber it when installing a bootstrap only
+.Pq Fl B ,
+or when editing an existing label
+.Pq Fl e ,
+but it unconditionally writes the primary bootstrap program onto
+the disk for
+.Fl w
+or
+.Fl R ,
+thus replacing the
+.Em fdisk
+table by the dummy one in the bootstrap program.  This is only of
+concern if the disk is fully dedicated, so that the BSD disklabel
+starts at absolute block 0 on the disk.