fix example in manpage, spotted by Jacek Masiulaniec

While there, stress the idea that users should always have a disklabel
inside their vnd images, so they can fsck their filesystems properly

input from otto@, corrections by jmc@, "looks better" deraadt@

1 files changed, 22 insertions, 8 deletions

diff --git a/sbin/mount_vnd/mount_vnd.8 b/sbin/mount_vnd/mount_vnd.8
index bce59aa80f9..470bb582ce5 100644
--- a/sbin/mount_vnd/mount_vnd.8
+++ b/sbin/mount_vnd/mount_vnd.8
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: mount_vnd.8,v 1.10 2007/09/29 07:10:09 fkr Exp $
+.\"	$OpenBSD: mount_vnd.8,v 1.11 2008/05/26 16:48:27 grunk Exp $
 .\"
 .\" Copyright (c) 1993 University of Utah.
 .\" Copyright (c) 1980, 1989, 1991, 1993
@@ -49,7 +49,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: September 29 2007 $
+.Dd $Mdocdate: May 26 2008 $
 .Dt MOUNT_VND 8
 .Os
 .Sh NAME
@@ -231,13 +231,15 @@ and mount the ISO 9660 file system contained in it:
 .Ed
 .Pp
 Configure an encrypted image file as vnode disk svnd0 and mount the FFS
-file system contained in it.
+file system contained in the
+.Sq a
+partition of the disklabel.
 The encryption key does not echo and must be entered every time
 the vnode disk is configured.
 .Bd -literal -offset indent
 # vnconfig -k svnd0 /tmp/cryptimg
 Encryption key:
-# mount /dev/svnd0c /mnt
+# mount /dev/svnd0a /mnt
 .Ed
 .Pp
 An equivalent
@@ -245,7 +247,7 @@ An equivalent
 entry is:
 .Bd -literal -offset indent
 /tmp/cryptimg /dev/svnd0c vnd rw,noauto,-k       0 0
-/dev/svnd0c   /mnt        ffs rw,noauto          0 0
+/dev/svnd0a   /mnt        ffs rw,noauto          0 0
 .Ed
 .Pp
 Same as above, but now configure the vnode using PKCS #5 PBKDF2 and
@@ -254,7 +256,7 @@ a salt file with 20000 rounds:
 # vnconfig -K 20000 svnd0 /tmp/cryptimg
 Encryption key:
 Salt file: /tmp/cryptsalt
-# mount /dev/svnd0c /mnt
+# mount /dev/svnd0a /mnt
 .Ed
 .Pp
 An equivalent
@@ -262,7 +264,7 @@ An equivalent
 entry is:
 .Bd -literal -offset indent
 /tmp/cryptimg /dev/svnd0c vnd rw,noauto,-K=20000 0 0
-/dev/svnd0c   /mnt        ffs rw,noauto          0 0
+/dev/svnd0a   /mnt        ffs rw,noauto          0 0
 .Ed
 .Pp
 Unmount the file system and unconfigure the vnode device:
@@ -279,7 +281,7 @@ in order to have vnd images configured at boot time is listed here:
 echo "configuring vnd devices:"
 mount /dev/svnd0c
 fsck -p /dev/svnd0a
-mount /mnt/svnd0a
+mount /mnt
 .Ed
 .Pp
 Mounting images during the first pass of
@@ -288,6 +290,18 @@ and
 .Xr mount 8
 is not possible, because the image to be configured to a vnd itself
 resides on a file system that first has to be checked and mounted.
+.Sh CAVEATS
+The
+.Sq c
+partition of a vnd image should not be used.
+When a superblock becomes damaged,
+.Xr fsck_ffs 8
+needs information contained in the disklabel
+to determine the location of alternate superblocks.
+This information is not available when directly using the
+.Sq c
+partition,
+so checking the filesystem image will fail.
 .Sh SEE ALSO
 .Xr vnd 4 ,
 .Xr fstab 5 ,