[Users] Linux sysprep

[Greg Padgett]

On 08/19/2013 04:26 PM, René Koch wrote:
>
> -----Original message-----
>> From:Greg Padgett <gpadgett at redhat.com>
>> Sent: Monday 19th August 2013 21:16
>> To: René Koch <r.koch at ovido.at>
>> Cc: ovirt-users <users at ovirt.org>
>> Subject: Re: [Users] Linux sysprep
>>
>> 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.
>
> Thanks a lot for your answer - this definitely points me into the right way.
>

Great, happy to help.

>
>>
>> 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.
>
>
> For some strange reason I totally missed the vm payload feature (and it seems to be introduced already in oVirt 3.1 according to the release notes).
> Can I attach a vm payload via webadmin portal of oVirt 3.2 (and if yes - how?) or only via REST-API?
>
> So if I understand this right, I would do the following:
> - use before_vm_start_hook which creates the payload and updates vm xml definition - add <payloads> with e.g. file name "unattended.txt" andcontent "hostname=pool-vm95"
> - have script started in host which mounts the floppy, reads the content of unattended.txt and do some magic
>

Only REST API.  It sounds like you're on the right track with it.

>
>
>>    - 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.
>
>
> cloud-init sounds very interesting, but this requires oVirt 3.3, right?
> I'm running oVirt 3.2 at the moment.
>

Yeah, 3.3 for the integrated features.  You could use it standalone in 
3.2, i.e. attach a config disk you made yourself--but compared to the 
approach above, the effort might not be worth it considering what you want 
to accomplish.

>
> Regards,
> René
>
>
>>
>> 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
>>
>>