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