[Users] Linux sysprep

[René Koch]

-----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.


> 
> 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



>   - 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.


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
> 
>