How to customize libvirt.xml for an instance ?

asked 2014-04-12 07:17:51 -0500

emanuele
11 ●1 ●1 ●2

updated 2014-04-14 12:36:54 -0500

larsks
5579 ●24 ●61 ●100 http://redhat.com/

Hello

I'm following the procedure at https://ask.openstack.org/en/question/5415/customize-libvirtxml-for-an-instance/ (https://ask.openstack.org/en/question...) but it doesn't seem to work. I'm on Havana.

This is what I see:

(1) No instance on the compute node

    root@node-12:~# virsh
    Welcome to virsh, the virtualization interactive terminal.

    Type:  'help' for help with commands
           'quit' to quit

virsh # list
 Id    Name                           State
----------------------------------------------------

(2) Create and boot an instance via Horizon, find the libvirt file and check it

virsh # list
 Id    Name                           State
----------------------------------------------------
 20    instance-0000000d              running

virsh #

root@node-12:~# ls -la /var/lib/nova/instances/
total 8
drwxr-xr-x  6 nova nova  136 Apr 12 11:50 .
drwxr-xr-x 10 nova nova  123 Mar 31 11:18 ..
drwxr-xr-x  2 nova nova   53 Apr 12 11:51 760a2891-da1a-40e1-b6de-ef6b9f029b09
more /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml
    <system>
      <entry name="manufacturer">OpenStack Foundation</entry>
      <entry name="product">OpenStack Nova</entry>
      <entry name="version">2013.2.2</entry>
      <entry name="serial">d289170a-baff-42d0-b858-2268192cc682</entry>
      <entry name="uuid">760a2891-da1a-40e1-b6de-ef6b9f029b09</entry>
    </system>

(3) Modify the libvirt file of the instance ( changed the value of entry name "product" ) and save the file

more /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml
<system>
      <entry name="manufacturer">OpenStack Foundation</entry>
      <entry name="product">Router in OpenStack Nova</entry>
      <entry name="version">2013.2.2</entry>
      <entry name="serial">d289170a-baff-42d0-b858-2268192cc682</entry>
      <entry name="uuid">760a2891-da1a-40e1-b6de-ef6b9f029b09</entry>
    </system>

(4) Follow the procedure explained at https://ask.openstack.org/en/question/5415/customize-libvirtxml-for-an-instance/ (https://ask.openstack.org/en/question...)

virsh # destroy instance-0000000d
Domain instance-0000000d destroyed

virsh # undefine instance-0000000d
Domain instance-0000000d has been undefined

virsh # define /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml
Domain instance-0000000d defined from /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml

virsh # start instance-0000000d
Domain instance-0000000d started

virsh # exit

(5) Check that the libvirt file is still modified, and then soft reboot (via Horizon) the instance

more /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml
    <system>
      <entry name="manufacturer">OpenStack Foundation</entry>
      <entry name="product">Router in OpenStack Nova</entry>
      <entry name="version">2013.2.2</entry>
      <entry name="serial">d289170a-baff-42d0-b858-2268192cc682</entry>
      <entry name="uuid">760a2891-da1a-40e1-b6de-ef6b9f029b09</entry>
    </system>

( soft reboot via Horizon )

(6) After soft reboot check the libvirt file; entry name "product" is back to the original value

more /var/lib/nova/instances/760a2891-da1a-40e1-b6de-ef6b9f029b09/libvirt.xml
    <system>
      <entry name="manufacturer">OpenStack Foundation</entry>
      <entry name="product">OpenStack Nova</entry>
      <entry name="version">2013.2.2</entry>
      <entry name="serial">d289170a-baff-42d0-b858-2268192cc682</entry>
      <entry name="uuid">760a2891-da1a-40e1-b6de-ef6b9f029b09</entry>
    </system>

Of course I don't really care about changing the entry name "product", but this is just to show that even what I believe was a cosmetic change is not possible (at least in my scenario)

Any suggestion ? Anybody able to reproduce the same behavior ?

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Comments

Hi, have you resolved the issue? I've the same problem.

UgoGio ( 2015-12-01 13:05:17 -0500 )edit

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4 answers

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answered 2015-02-15 00:04:10 -0500

championofcyrodiil
41 ●1 ●2 ●4 http://championofcyrod...

some settings, such as hardware video driver cirrus, vesa, or qxl. can be defined in the glance image metadata. However, this likely will need to be supported through libvirt. I have been able to get qxl and video ram modified this way in Icehouse.

I also had to modify the flavor's max video ram size.

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hmmm, do you have any more detail informations? is there an given list for valid metadata? maybe you can give an example how to change the system product name?

Volker ( 2019-02-14 14:48:59 -0500 )edit

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answered 2014-04-14 00:05:45 -0500

waqasriaz

100 ●4 ●6 ●14

updated 2014-04-15 10:16:38 -0500

I faced the same problem. I found out that restarting VM via openstack drops the changes in libvirt xml.

Rebooting from virsh after changing libvirt xml will not undo the changes. e.g

virsh reboot instance-0000000d

However if you want to add your customization through openstack, you may add your changes in following files.

libvirt xml is created in nova/virt/libvirt/driver.py and its configuration classes are defined in nova/virt/libvirt/config.py

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Ok ... for the records here is the result

virsh # reboot instance-0000000d
error: Failed to reboot domain instance-0000000d
error: Requested operation is not valid: Reboot is not supported without the JSON monitor

virsh # list
Id    Name                           State
----------------------------------------------------

Googling around it seems I would need to rebuilt libvirt manually to include yajl-devel libraries ....

Before I go on and try to do that, allow me one question: where does Openstack define the libvirt.xml template that is enforced everytime an instance is booted/rebooted ?

emanuele ( 2014-04-15 02:17:53 -0500 )edit

libvirt xml is created in nova/virt/libvirt/driver.py and its configuration classes are defined in nova/virt/libvirt/config.py .... if you want to add your customization through openstack, you may add your changes in these files.

waqasriaz ( 2014-04-15 10:17:16 -0500 )edit

Perfect, nova resize may fail while increasing the memory(RAM) with CPU pinning. Updated /usr/lib/python2.7/dist-packages/nova/virt/libvirt/driver.py function _get_cpu_numa_config_from_instance with a if condition to match memory.