switch_root: add note about subroots to switch_root.8

Based on patch from Daniel Drake <dsd@laptop.org>

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/switch_root.8 b/sys-utils/switch_root.8
index 4fdc8e9459735a22b791e24ecf19b78e0a3e85cb..b6712ecb1afa7453ac8463cb5cf73edb471f8586 100644 (file)
--- a/sys-utils/switch_root.8
+++ b/sys-utils/switch_root.8
@@ -32,6 +32,19 @@ show version number and exit
 .B switch_root
 returns 0 on success and 1 on failure.
 
+.SH NOTES
+switch_root will fail to function if
+.B newroot
+is not the root of a mount. If you want to switch root into a directory that
+does not meet this requirement then you can first use a bind-mounting trick to
+turn any directory into a mount point:
+.sp
+.nf
+.RS
+mount --bind $DIR $DIR
+.RE
+.fi
+
 .SH "SEE ALSO"
 .BR mount (8)
 .BR chroot (2)