[Libvir] [RFC] Add Container support to libvirt

[Dave Leskovec]

Balbir,

I'd appreciate any links...

How will this configuration be persisted across reboots?  Specifically, 
once a configuration is set up for a container, who is responsible for 
storing this configuration?  Will a libvirt driver need to store it 
somewhere in it's configuration file(s) or will it be stored somewhere 
else by a resource management facility such that it can associated it 
with a container after a reboot?

Balbir Singh wrote:
> * Daniel P. Berrange <berrange at redhat.com> [2008-01-15 15:52:13]:
>
>   
>> On Tue, Jan 15, 2008 at 12:26:43AM -0800, Dave Leskovec wrote:
>>     
>>> Greetings,
>>>
>>> Following up on the XML format for the Linux Container support I 
>>> proposed...  I've made the following recommended changes:
>>> * Changed mount tags
>>> * Changed nameserver tag to be consistent with gateway
>>> * Moved cpushare and memory tags outside container tag
>>>
>>> This is the updated format:
>>> <domain type='linuxcontainer'>
>>>   <name>Container123</name>
>>>   <uuid>8dfd44b31e76d8d335150a2d98211ea0</uuid>
>>>   <container>
>>>       <filesystem>
>>>           <mount>
>>>               <source dir="/home/user/lxc_files/etc/"/>
>>>               <target dir="/etc/"/>
>>>           </mount>
>>>           <mount>
>>>               <source dir="/home/user/lxc_files/var/"/>
>>>               <target dir="/var/"/>
>>>           </mount>
>>>       </filesystem>
>>>       
>> Comparing this to the Linux-VServer XML that Daniel posted, you're both
>> pretty much representing the same concepts so we need to make a decision
>> about which format to use for  filesystem mounts.
>>
>> OpenVZ also provides a /domain/container/filesystem tag, though it
>> uses a concept of filesystem templates auto-cloned per container
>> rather than explicit mounts. I think I'd like to see
>>
>>        <filesystem type="mount">
>>                <source dir="/home/user/lxc_files/etc/"/>
>>                <target dir="/etc/"/>
>>        </filesystem>
>>
>> For the existing OpenVZ XML, we can augment their <filesystem> tag with
>> an attribute  type="template".
>>
>>     
>>>       <application>/usr/sbin/container_init</application>
>>>       <network hostname='browndog'>
>>>           <ip address="192.168.1.110" netmask="255.255.255.0"/>
>>>               <gateway address="192.168.1.1"/>
>>>               <nameserver address="192.168.1.1"/nameserver>
>>>           </ip>
>>>       </network>
>>>       
>> Again this is pretty similar to needs of VServer / OpenVZ. In the existing
>> OpenVZ XML, the gateway and nameserver tags are immediately within the
>> <network> tag, rather than nested inside the <ip> tag. Aside from that it
>> looks to be a consistent set of information.
>>
>>     
>>>   </container>
>>>   <cpushare>40</cpushare>
>>>       
>> As Daniel points out, we've thus far explicitly excluded tuning info from
>> the XML. Not that I have any suggestion on where else to put it at this
>> time. This is a minor thing though, easily implemented once we come to a
>> decision.
>>     
>
> At some point, we'll need resource management extensions to libvirt.
> vserver and openVZ both use them and it will also be useful for
> containers and kvm/qemu as well. I think we'll need a resource
> management feature extension to the XML format.
>
> Currently resource management is provided through control groups (I
> can send out links if desired). Ideally once configured the control
> groups should be persistent (visible across reboots, so we need to
> save state).
>
> Thoughts?
>
>   
>>>   <memory>65536</memory>
>>>   <devices>
>>>       <console tty='/dev/pts/4'/>
>>>   </devices>
>>> </domain>
>>>
>>> Does this look ok now?  All comments and questions are welcome.
>>>       
>> Pretty close.
>>
>> Dan.
>> -- 
>> |=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
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>>
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>>     
>
>   

-- 
Best Regards,
Dave Leskovec
IBM Linux Technology Center
Open Virtualization