[src/trunk]: src/sbin/umount Document external unmount programs. PR 698. Bump...

[dholland <dholland%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3cc2d48de935
branches:  trunk
changeset: 346106:3cc2d48de935
user:      dholland <dholland%NetBSD.org@localhost>
date:      Sun Jun 26 03:59:11 2016 +0000

description:
Document external unmount programs. PR 698. Bump date.

diffstat:

 sbin/umount/umount.8 |  23 ++++++++++++++++++++---
 1 files changed, 20 insertions(+), 3 deletions(-)

diffs (58 lines):

diff -r 0aa1bf9bc0cf -r 3cc2d48de935 sbin/umount/umount.8
--- a/sbin/umount/umount.8      Sun Jun 26 03:51:28 2016 +0000
+++ b/sbin/umount/umount.8      Sun Jun 26 03:59:11 2016 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: umount.8,v 1.15 2009/05/17 14:09:15 mjf Exp $
+.\"    $NetBSD: umount.8,v 1.16 2016/06/26 03:59:11 dholland Exp $
 .\"
 .\" Copyright (c) 1980, 1989, 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)umount.8   8.2 (Berkeley) 5/8/95
 .\"
-.Dd May 17, 2009
+.Dd June 26, 2016
 .Dt UMOUNT 8
 .Os
 .Sh NAME
@@ -51,7 +51,7 @@
 command
 calls the
 .Xr unmount 2
-system call to remove a
+system call (or an external unmount program) to remove a
 .Ar "special device"
 or the remote node (rhost:path) from the filesystem tree at the point
 .Ar node .
@@ -63,6 +63,22 @@
 .Xr fstab 5
 file.
 .Pp
+By default, the file system type is extracted from the kernel and used
+to choose an external unmount program, whose name is formed by
+appending an underscore and the type string to
+.Dq umount .
+This matches the form used by the external mount programs used by
+.Xr mount 8 .
+If this program is found on the path, it is used in preference to
+calling
+.Xr unmount 2
+directly.
+Note that in the
+.Nx
+base system no such external unmount programs exist; the
+facility is provided in the hopes that it will be useful for third
+party file systems and/or for research.
+.Pp
 The options are as follows:
 .Bl -tag -width indent
 .It Fl a
@@ -97,6 +113,7 @@
 This is the only way to unmount something that does not appear as a
 directory (such as a nullfs mount of a plain file); there are probably
 other cases where it is necessary.
+This option also disables the use of any external unmount program.
 .It Fl h Ar host
 Only filesystems mounted from the specified host will be
 unmounted.