ad9577
From 0ae2aa6a43a852cb0326faade1532c02aa7617a4 Mon Sep 17 00:00:00 2001
ad9577
From: Karel Zak <kzak@redhat.com>
ad9577
Date: Fri, 20 Apr 2018 09:50:04 +0200
ad9577
Subject: [PATCH 156/173] umount: add note about --lazy
ad9577
ad9577
Unfortunately, it's pretty common that users on production systems use
ad9577
lazy umount to fix some FS issues. The usual result is unwanted system
ad9577
reboot, because -l is not the right way how to fix unreachable NFS or
ad9577
mess with local FS with submounts.
ad9577
ad9577
Note that after lazy umount /proc/self/mountinfo does not contain the
ad9577
FS entry, but kernel still references the FS. It makes it very
ad9577
difficult to debug.
ad9577
ad9577
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1566674
ad9577
Suggested-by:  Steve Dickson <steved@redhat.com>
ad9577
Signed-off-by: Karel Zak <kzak@redhat.com>
ad9577
Upstream: http://github.com/karelzak/util-linux/commit/031800ff6c66b4d62229cfd116195950a718a21c
ad9577
---
ad9577
 sys-utils/umount.8 | 10 +++++++++-
ad9577
 1 file changed, 9 insertions(+), 1 deletion(-)
ad9577
ad9577
diff --git a/sys-utils/umount.8 b/sys-utils/umount.8
ad9577
index f0a712b06..71c2155b4 100644
ad9577
--- a/sys-utils/umount.8
ad9577
+++ b/sys-utils/umount.8
ad9577
@@ -54,7 +54,8 @@ working directory there, or when a swap file on it is in use.  The
ad9577
 offending process could even be
ad9577
 .B umount
ad9577
 itself - it opens libc, and libc in its turn may open for example locale
ad9577
-files.  A lazy unmount avoids this problem.
ad9577
+files.  A lazy unmount avoids this problem, but it may introduce another
ad9577
+issues. See \fB\-\-lazy\fR description bellow.
ad9577
 .SH OPTIONS
ad9577
 .TP
ad9577
 \fB\-a\fR, \fB\-\-all\fR
ad9577
@@ -107,6 +108,13 @@ Unmount without writing in
ad9577
 Lazy unmount.  Detach the filesystem from the filesystem hierarchy now,
ad9577
 and cleanup all references to the filesystem as soon as it is not busy
ad9577
 anymore.  (Requires kernel 2.4.11 or later.)
ad9577
+
ad9577
+A system reboot would be expected in near future if you're going to use this
ad9577
+option for network filesystem or local filesystem with submounts.  The
ad9577
+recommended use-case for \fBumount -l\fR is to prevent hangs on shutdown due to
ad9577
+an unreachable network share where a normal umount will hang due to a downed
ad9577
+server or a network partition. Remounts of the share will not be possible.
ad9577
+
ad9577
 .TP
ad9577
 \fB\-O\fR, \fB\-\-test\-opts\fR \fIoptions,list\fR
ad9577
 Indicate that the actions should only be taken on file systems with the
ad9577
-- 
ad9577
2.14.4
ad9577