[one-users] DHCP

kerryhall . kerryhall at gmail.com
Thu Jul 24 12:36:57 PDT 2014


Thank you for the help!

Yes, AFAIK the DNS server is configured with a dynamic zone that is updated
from the DHCP server.

It sounds like the DHCP server in use is Microsoft DHCP. I would like to
avoid using the DHCP API if possible, just because I have no experience in
that area, and seems like a messy solution.

Thinking about this more, here are the desired steps:
1. User spins up vm via web interface.
2. Contextualization sets "DHCP_HOSTNAME" to vm name.
3. DHCP server gives vm an IP address.
4. Sunstone sets the correct IP information in its database.

I can basically do all this manually by
1. Spin up vm
2. edit ifcfg-eth0, setting BOOTPROTO and DHCP_HOSTNAME
3. restart networking

So it sounds like I can write a bash script that takes care of 2. and 3.,
something that runs when the vm is spun up.

However, I don't know how to manually tell Sunstone what the new, correct
IP is. Do you know how I could accomplish that?

I can write a bash or perl script that fixes this manually in MySQL....but
that seems like a Really Bad Idea. :)

I'm surprised that OpenNebula doesn't support DHCP out of the box. Seems
like a common use case. I wonder if I should make a feature request.


On Wed, Jul 23, 2014 at 10:03 PM, Valentin Bud <valentin.bud at gmail.com>

> Hello Kerry,
> When you say "DNS and DHCP are tied into one system on my network" you mean
> your DNS server is configured with a dynamic zone that is updated from the
> server?
> If that is so, I guess you want a VM to acquire a lease from the DHCP
> server equal
> to the IP given by OpenNebula to that specific VM. This way it maintains
> consistency.
> If you populate CONTEXT with NETWORK="YES", the contextualization packages
> will do the job of configuring the network. As far as I know it's not
> possible to "tell"
> the contextualization packages to leave the network unconfigured. So using
> this approach
> would not get you where you want.
> One way of achieving what you desire is to program a hook that inserts a
> host in the
> DHCP server via OMAPI [1]. From the hook you have access to the entire
> template.
> I am assuming you are using ISC DHCP. This would solve the consistency
> issue.
> Now the VM needs to be configured for DHCP as you mentioned in your
> previous E-Mail.
> For that you can define SET_HOSTNAME in the CONTEXT to have it available
> in the
> VM, create a simple (bash) program that reads it and sets ifcfg-eth0
> accordingly. Put the
> script in the files datastore and update the context to use it via
> For example you name your super script set_dhcp.sh. You can insert in the
> files datastore [2]
> using `oneimage create -d files --name set_dhcp.sh --type CONTEXT
> /path/to/set_dhcp.sh`.
> Update the template to use it.
> FILES_DS="$FILE[IMAGE=\"set_dhcp.sh\",
> INIT_SCRIPTS="set_dhcp.sh"]
> This way the vmcontext init.d script from the contextualization packages
> would skip the
> network configuration, note NETWORK="YES" is missing and it would run the
> set_dhcp.sh
> script.
> One more thing that comes to mind, SET_HOSTNAME would instruct the
> vmcontext init
> script to set the hostname and maybe that's not what you want, maybe you
> want your VM
> to set it's hostname from DHCP. In this case use another variable, like
> in CONTEXT and process it in set_dhcp.sh to configure ifcfg-eth0.
> You can set DHCP_HOSTNAME=$NAME inside the template. This way the name you
> give the VM in Sunstone would end up being used.
> Take the above with a grain of salt, I am sure there are other (better)
> ways of achieving
> what you desire.
> @Diego could you please point me where have you find DHCP in the VNET
> template?
> I have looked over the docs and couldn't find it.
> [1]: http://ipamworldwide.com/dhcp-api.html
> [2]: http://docs.opennebula.org/4.6/administration/storage/file_ds.html
> Best,
> Valentin
> On Wed, Jul 23, 2014 at 10:45 PM, kerryhall . <kerryhall at gmail.com> wrote:
>> I have managed to figure out how to edit my template (onetemplate update
>> TEMPLATE_ID) so I can now set the hostname. However, DNS and DHCP are tied
>> into one system on my network, so I can't perform a dig on my new server
>> and get the IP back.
>> I just need to know what lines to add to my template file to get my vms
>> to use DHCP only. I'm sure it's something really simple, I just can't find
>> any info here:
>> http://docs.opennebula.org/4.6/user/virtual_machine_setup/cong.html
>> If you know how to get DHCP working, please let me know.
>> Thank you!!
>> On Tue, Jul 22, 2014 at 3:48 PM, kerryhall . <kerryhall at gmail.com> wrote:
>>> Hi folks,
>>> I want to configure Open Nebula to contextualize two items for
>>> ifcfg-eth0.
>>> BOOTPROTO=dhcp
>>> and
>>> DHCP_HOSTNAME=<parameter passed in via ONE web interface, even just
>>> vm-name would work>
>>> I need no other networking settings. DHCP on my network handles the
>>> rest. I have tried manually setting these two parameters in ifcfg-eth0 and
>>> it looks like it works. (Although the new IP given via DHCP doesn't match
>>> the original IP)
>>> Is this possible to do in ONE? If so, where do I start?
>>> Thanks!
>>> Kerry
>> _______________________________________________
>> Users mailing list
>> Users at lists.opennebula.org
>> http://lists.opennebula.org/listinfo.cgi/users-opennebula.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opennebula.org/pipermail/users-opennebula.org/attachments/20140724/35a36e16/attachment.htm>

More information about the Users mailing list