Add a sentence to the umount.8 man page to clarify the behaviour

for forced dismount when used on an NFS mount point. Requested by
Jeremy Chadwick.
This is a content change.

MFC after:	2 weeks

1 files changed, 4 insertions, 1 deletions

diff --git a/sbin/umount/umount.8 b/sbin/umount/umount.8
index 91231a7..cb3a97b 100644
--- a/sbin/umount/umount.8
+++ b/sbin/umount/umount.8
@@ -28,7 +28,7 @@
 .\"     @(#)umount.8	8.2 (Berkeley) 5/8/95
 .\" $FreeBSD$
 .\"
-.Dd July 18, 2003
+.Dd May 31, 2011
 .Dt UMOUNT 8
 .Os
 .Sh NAME
@@ -78,6 +78,9 @@ The file system is forcibly unmounted.
 Active special devices continue to work,
 but all other files return errors if further accesses are attempted.
 The root file system cannot be forcibly unmounted.
+For NFS, a forced dismount can take up to 1 minute or more to
+complete against an unresponsive server and may throw away
+data not yet written to the server for this case.
 .It Fl h Ar host
 Only file systems mounted from the specified host will be
 unmounted.