[Users] Linux sysprep

[Greg Padgett]

On 08/19/2013 10:17 AM, René Koch (ovido) wrote:
> Hi,
>
> Has anyone an idea what's the easiest way to sysprep Linux (CentOS 6 and
> RHEL 6) machines?
>
> The use case is the following: I want to create a lot of virtual
> machines (e.g. 100) by cloning from one template.
> So I create a master vm, create a template and a pool with 100 vms
> assigned to it and set all 100 vms to prestarted.
>
> The problem is now, that when I run "sys-unconfig" before creating the
> template, which does a "touch /.unconfigured" I have to go through the
> sysconfig-tui and set a new root password for all 100 hosts.
>
> So what I'm looking for is a script like the sysprep tool for windows
> which sets parameters for me automatically.
> I only need to change:
> * Hostname + set DHCP_HOSTNAME in ifcfg-eth0 (Hostname == Pool-VM-Name)
> for some dhcp/ddns magic :)
> * Clear udev network-rules
> * remove SSH-Keys
> * Remove RHN ID and join Satellite/Spacewalk-server
> * root-password,... should stay the same
>
> My first question is: does oVirt provide such a functionality for Linux
> guest out-of-the-box? I couldn't find one.
>
>
> I think I could solve this with virt-sysprep and virt-file, but I'm
> unsure if I can use it with oVirt (or only with plain libvirt):
> http://libguestfs.org/virt-sysprep.1.html
> http://libguestfs.org/virt-edit.1.html
>
> For this tools it's required that the vm is not running, as it changes
> files on the disk. If I'm using a before-vm-start hook, it should be
> save to access the disk and change content with virt-sysprep/virt-file,
> right?
> But do I have access to the disk in a before-vm-start hook?
> If using NFS storage I should be able to access all disks on the
> NFS-share, but for iSCSI/FC-LUNS - are they available on the hypervisor
> in this stage?
>
>
> Another option would be to write a custom script which is started during
> boot and disables itself after successful run (in the same way as
> firstboot - I already have such a script for RHN Satellite/Spacewalk
> joins). The problem here is: How do I get the (oVirt) name of this vm
> (would need something like virt-whoami :) )? Is the (internal oVirt) ID
> of this vm stored somewhere in the filesystem of this vm? I don't think
> so....
>
>
> Thanks a lot for suggestions,
> René
>

Hi René,

You may be able to accomplish at least some of what you want using 
Cloud-Init, some features of which we've integrated into oVirt [1].  It 
went in recently so may not be in whichever version you're running, but 
you can probably borrow some of the concepts to get the job done.

Just a few ideas:
  - create a vm payload [2] and attach it to the VM which can hold your 
config info e.g. vm name, which a custom script could pick up.  No need 
for the latest oVirt with this option.
  - create a Cloud-Init config disk yourself and attach it as a payload, 
and let Cloud-Init do the initialization.  There are several formats; 
oVirt uses Config-Drive-v2.  Example at [3].  Depending on the config disk 
format, you may need the latest oVirt/vdsm to assign a volume label to the 
vm payload.
  - use the latest oVirt and its Cloud-Init functionality; for fields not 
handled, attach a file and let a script handle it.

HTH,
Greg

[1] http://www.ovirt.org/Features/Cloud-Init_Integration
[2] http://www.ovirt.org/Features/VMPayload
[3] 
http://docs.openstack.org/trunk/openstack-compute/admin/content/config-drive.html