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

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Richard W.M. Jones
2012-07-28 21:28:23 +01:00
parent dcc0ebc8e0
commit b61a8a50bc
1 changed files with 24 additions and 14 deletions
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sysprep/virt-sysprep.pod
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@@ -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 *