sysprep: Describe more directly how to use qemu-img for snapshotting.

1 files changed, 24 insertions, 14 deletions

diff --git a/sysprep/virt-sysprep.pod b/sysprep/virt-sysprep.pod
index 9172931d..66bc7104 100755
--- a/sysprep/virt-sysprep.pod
+++ b/sysprep/virt-sysprep.pod
@@ -20,7 +20,7 @@ required.
 
 Virt-sysprep modifies the guest or disk image I<in place>.  The guest
 must be shut down.  If you want to preserve the existing contents of
-the guest, you I<must copy or clone the disk first>.
+the guest, you I<must snapshot, copy or clone the disk first>.
 See L</COPYING AND CLONING> below.
 
 You do I<not> need to run virt-sysprep as root.  In fact we'd
@@ -304,33 +304,43 @@ L<cp(1)> or L<dd(1)>.
 
 There are some smarter (and faster) ways too:
 
-=over 4
-
-=item *
-
                           snapshot
                 template ---------->
                             \------> cloned
                              \-----> guests
                               \---->
 
-Use the block device as a backing file and create a snapshot on top
-for each guest.  The advantage is that you don't need to copy the
-block device (very fast) and only changes are stored (less storage
-required).
+=over 4
+
+=item *
+
+Create a snapshot using qemu-img:
+
+ qemu-img create -f qcow2 -o backing_file=original snapshot.qcow
+
+The advantage is that you don't need to copy the original (very fast)
+and only changes are stored (less storage required).
 
 Note that writing to the backing file once you have created guests on
 top of it is not possible: you will corrupt the guests.
 
-Tools that can do this include:
-L<qemu-img(1)> (with the I<create -f qcow2 -o backing_file> option),
-L<lvcreate(8)> (I<--snapshot> option).  Some filesystems (such as
-btrfs) and most Network Attached Storage devices can also create cheap
+=item *
+
+Create a snapshot using C<lvcreate --snapshot>.
+
+=item *
+
+Other ways to create snapshots include using filesystems-level tools
+(for filesystems such as btrfs).
+
+Most Network Attached Storage (NAS) devices can also create cheap
 snapshots from files or LUNs.
 
 =item *
 
-Get your NAS to snapshot and/or duplicate the LUN.
+Get your NAS to duplicate the LUN.  Most NAS devices can also
+duplicate LUNs very cheaply (they copy them on-demand in the
+background).
 
 =item *