From: Sami Kerola <kerolasa@iki.fi>
Date: Sun, 7 Jun 2015 20:51:51 +0000 (+0100)
Subject: docs: unify mkswap(8) with swapon(8) about holes warning
X-Git-Tag: v2.27-rc1~120
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=55034ed00e94657109eb0405b65086f1d3e91423;p=thirdparty%2Futil-linux.git

docs: unify mkswap(8) with swapon(8) about holes warning

Reviewed-by: Dave Rutherford <dave@evilpettingzoo.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---

diff --git a/disk-utils/mkswap.8 b/disk-utils/mkswap.8
index 0a0b715dd5..3655357bd0 100644
--- a/disk-utils/mkswap.8
+++ b/disk-utils/mkswap.8
@@ -128,9 +128,19 @@ e.g.\& using a command like
 .RE
 .fi
 
-Note that a swap file must not contain any holes (so, using
+Note that a swap file must not contain any holes.  Using
 .BR cp (1)
-to create the file is not acceptable).
+to create the file is not acceptable.  Neither is use of
+.BR fallocate (1)
+on file systems that support preallocated files, such as
+.BR XFS " or " ext4 ,
+or on copy-on-write filesystems like
+.BR btrfs .
+It is recommended to use
+.BR dd (1)
+and /dev/zero in these cases.  Please read notes from
+.BR swapon (8)
+before adding a swap file to copy-on-write filesystems.
 
 .SH ENVIRONMENT
 .IP LIBBLKID_DEBUG=all