Virt Tools Survey: What to do about virt-clone

[Richard W.M. Jones]

I've volunteered for the task of fixing virt-clone[0].  There are a
number of bugs which need to be addressed.  Unfortunately the current
virt-clone is broken-by-design since it cannot make changes inside the
guest.

  [0] http://linux.die.net/man/1/virt-clone

The bugs boil down to what Microsoft calls "sysprepping" the clone,
which is to say, removing its existing identity, hostname, ssh host
keys, persistent network rules, host SID and workgroup name (for
Windows).  It's helpful for Linux guests to remove some of this
stuff[1] -- it will make the cloning process smoother.  For Windows
it's absolutely required[2].

  [1] https://rwmj.wordpress.com/2010/09/24/tip-my-procedure-for-cloning-a-fedo...
  [2] http://technet.microsoft.com/en-us/library/cc721940%28WS.10%29.aspx

All that virt-clone can do now is to copy the guest and make some
simple changes to the libvirt XML (eg. giving it a new MAC address).
It doesn't even address the sysprepping problem.

The problem with sysprepping is that it's hard to do, and it's
different for every operating system.  I've summarized some of the
techniques below.  Worse than that, for some OSes there are different
levels of sysprepping that an administrator might want; also see
below.

So I'd like feedback from "virt-clone next generation" users:

(a) Is cloning guests useful for you or not?  Often or infrequently?

(b) Do you currently use virt-clone to clone guests?

(c) Do you have a homebrew method to clone guests?  What does it do?

(d) Do you use another tool to clone guests?  (And how is it?)

(e) When you clone a guest, do you "sysprep" it or would you like to?
(Using the term "sysprep" generically here, I mean any sort of
reinitialization for Linux or Windows guests).

(f) How do you feel about a multi-step process?

  virt-clone -> virt-sysprep -> virt-resize (for example)

(g) Have you had other problems with cloning guests?

(h) What have I missed out in this analysis?  What other features have
you missed in virt-clone?

Sysprepping Windows
-------------------

This is a complex, manual process.  We do some steps to automate it in
RHEV.  It's best to read Microsoft's online documentation at
[2][3][4].

  [3] http://support.microsoft.com/kb/302577
  [4] http://blogs.technet.com/b/megand/archive/2005/01/20/357570.aspx

Fedora
------

In theory you can just write a file /.unconfigured in the root, and
Fedora will go through the firstboot process at next boot (it will
reset timezone, root password, netconfig, keyboard, authentication).

Some admins will *not* want all of these things to be reset, and will
want either a lesser degree of unconfiguration, or will want to
control each thing manually.

I'm not totally convinced that this hasn't been broken by systemd
introduction in Fedora 15.

general Linux
-------------

See [1].

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://et.redhat.com/~rjones/virt-df/

[Tom Horsley]

On Tue, 10 May 2011 12:56:30 +0100
Richard W.M. Jones wrote:

>  (c) Do you have a homebrew method to clone guests?  What does it do?
I'm in the middle of devising a home brew clone script strictly for
a Windows XP machine KVM I sometimes need extra copies of.

I have a readonly qcow2 image I use as a backing file for making
new qcow2 images for the clones. I've manually changed the
computer name and default screen background and gotten diffs
showing the registry changes made (there are a fantastic
number of them, which was hard to believe).

I'm about try try using the virt-win-reg tool on one of the
new qcow2 images to modify the registry and give the machine
a new identity before I boot it (but I haven't quite gotten
around try trying it yet).

[Chris Lalancette]

On 05/10/11 - 12:56:30PM, Richard W.M. Jones wrote:
>  Sysprepping Windows
>  -------------------
>  
>  This is a complex, manual process.  We do some steps to automate it in
>  RHEV.  It's best to read Microsoft's online documentation at
>  [2][3][4].
>  
>    [3] http://support.microsoft.com/kb/302577
>    [4] http://blogs.technet.com/b/megand/archive/2005/01/20/357570.aspx 
Note that Oz[1] can do some of this.  There is a side-branch of Oz called
"win2k8customize" that has some of this sysprepping functionality built-in.
It's not on master at the moment because it requires something of a hacked-up
tool called "winexe", but we are in the process of finding a replacement
for "winexe" at the moment.

-- 
Chris Lalancette

[1] http://aeolusproject.org/oz.html

[Qemu-devel] Virt Tools Survey: What to do about virt-clone

[Gerd Hoffmann]

   Hi,

>  (a) Is cloning guests useful for you or not?  Often or infrequently?
I'm almost never do that.

Usually I use qcow2 copy-on-write images for testing, so I can easily 
rollback stuff by just zapping and re-creating the copy-on-write image.

When I need a fresh VM I install one.  Have kickstart in place for 
RHEL/Fedora guests.  Also a custom windows xp install cd which 
autoinstalls via unattended.txt, so I don't have to babysit the 
installs.  Includes sp3 and some extra drivers (e1000, virtio-net, ...) too.

cheers,
   Gerd

[virt-tools-list] Virt Tools Survey: What to do about virt-clone

[Alexander Boström]

On tis, 2011-05-10 at 12:56 +0100, Richard W.M. Jones wrote:

>  Fedora
>  ------
>  
>  In theory you can just write a file /.unconfigured in the root, and 
Perhaps this could also be triggered by a change in the system UUID (see
dmidecode). Store the UUID in a file during kickstart/firstboot and
check it at every boot. If it changed then the disk was either moved or
cloned to new hardware (physical or virtual doesn't really matter), so
perhaps the system could ask for a root password and after confirmation
start the re-setup process.

>  Some admins will *not* want all of these things to be reset, and
> will
>  want either a lesser degree of unconfiguration, or will want to
>  control each thing manually. 
Yeah, it's rather analogous to kickstart.

I think every guest OS needs to have support for this internally because
it gets too complicated to do it from the outside but it should be
possible to trigger the process and control it using the virt tools.

The OS needs to back out some changes from the system and then redo part
of the kickstart/firstboot. (The division between Anaconda and Firstboot
seems a bit arbitrary, so I'm treating them as one thing here.)

Stuff that can happen at boot after cloning:

1. (If virt-clone triggered the boot, skip this step.)
Ask the admin if this is a clone or a move. If it's a move, exit and
continue with the normal boot. Otherwise, ask for the root password.

2. Eradicate as thoroughly as possible any host-private data. This can
be Smolt ID, Spacewalk, RHN data, SSH key pairs, Kerberos keys, Puppet
registration, reset the hostname to localhost.localdomain and so on.

3. Forget about any hardware that doesn't seem to exist anymore (so eth0
is removed from udev and the configuration is deleted from NM).

4. At this point it should be possible to shut down, thereby creating a
clean slate template.

5. Re-run some parts of kickstart/firstboot. This should be scriptable
and virt-clone should be able to provide this info.
* Network config.
* (Hash of) the root password, bootloader password.
* Smolt, Kerberos hostkey, Spacewalk, RHN, Puppet...
* %post script.

/abo

[Athmane Madjoudj]

On 05/10/2011 12:56 PM, Richard W.M. Jones wrote:
>  So I'd like feedback from "virt-clone next generation" users:
>
>  (a) Is cloning guests useful for you or not?  Often or infrequently?
>  
Yes, I use it often, at work (Linux SysAdmin) and during Fedora testing 
cycle (Alpha, Beta, RC etc...).

>  (b) Do you currently use virt-clone to clone guests?
>  
Yes, until bug rhbz#667509 appears.

>  (c) Do you have a homebrew method to clone guests?  What does it do?
>  
Yes, it a small shell script, that copy the guest image, create a new 
guest with virt-install  --import ...

>  (d) Do you use another tool to clone guests?  (And how is it?)
>  
No.

>  (e) When you clone a guest, do you "sysprep" it or would
> you like to?
>  (Using the term "sysprep" generically here, I mean any sort of
>  reinitialization for Linux or Windows guests).
>  
No.

>  (f) How do you feel about a multi-step process?
>
>     virt-clone ->  virt-sysprep ->  virt-resize (for example) 
If virt-{clone,sysprep,resize} are separate tool then it very good idea 
otherwise (ie: one monolithic app) it's over-engineered.

>  (g) Have you had other problems with cloning guests?
>  
Yes, bug rhbz#667509


>  (h) What have I missed out in this analysis?  What other features
> have
>  you missed in virt-clone?
>  
PS.
AFAIK, cloning on VMware does not touch the inside of the guest

-- 
Athmane Madjoudj
RHCE