libvirt users - Mar 2016 - Re: which is the config file for a vm ?

Hi, 

i have a weird problem. I have a vm (KVM) which seems to run fine. I believe the
respective config file for this vm is /etc/libvirt/qemu/MausDB.xml. This is it:

========================================================<domain
type='kvm'>
  <name>MausDB</name>
  <uuid>d4c7956c-b57f-967a-0454-99835a3a740b</uuid>
  <memory unit='KiB'>2353792</memory>
  <currentMemory unit='KiB'>2353792</currentMemory>
  <vcpu placement='static'>2</vcpu>
  <os>
    <type arch='x86_64'
machine='pc-i440fx-1.4'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/bin/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/kvm/images/MausDB/disk0.raw'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x04' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hda' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='0'
target='0' unit='0'/>
    </disk>
    <controller type='usb' index='0'>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x01' function='0x2'/>
    </controller>
    <controller type='pci' index='0'
model='pci-root'/>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x01' function='0x1'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:37:92:03'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x03' function='0x0'/>
    </interface>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='-1'
autoport='yes'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x05' function='0x0'/>
    </memballoon>
  </devices>
</domain>
============================================================
As you see, the vm has one NIC. Its MAC-Address is: '52:54:00:37:92:03'.
I also see that MAC when i edit the config via virsh.

But when i boot that vm, it has a nic with another MAC:
'52:54:00:37:92:B2' ??? lspci shows me just one nic in the vm.
This MAC-Address is also visible in the Virtual Machine Manager.
Pictures you find here: https://hmgubox.helmholtz-muenchen.de:8001/d/51feb02c02/
I thought the xml-file in /etc/libvirt/qemu ist the only responsable one. It is
that one which is configured when i issue a 'edit domain' in virsh. Or ?
Where does the VMM stores the configuration of the domains ?
I found another xml: /var/run/libvirt/qemu/MausDB.xml . Inside it there is the
MAC the booted vm has. What is the purpose of this xml ?
Also ps inside the host shows the MAC which is in the booted vm:

root     28237  4.8  2.4 2886084 2416116 ?     Sl   Feb29  55:16
/usr/bin/qemu-kvm -name MausDB -S -machine pc-i440fx-1.4,accel=kvm,usb=off -m
2299 -smp 2,sockets=2,cores=1,threads=1 -uuid
d4c7956c-b57f-967a-0454-99835a3a740b -no-user-config -nodefaults -chardev
socket,id=charmonitor,path=/var/lib/libvirt/qemu/MausDB.monitor,server,nowait
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown
-boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive
file=/var/lib/kvm/images/MausDB/disk0.raw,if=none,id=drive-virtio-disk0,format=raw
-device
virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
-drive if=none,id=drive-ide0-0-0,readonly=on,format=raw -device
ide-cd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev
tap,fd=22,id=hostnet0,vhost=on,vhostfd=23 -device
virtio-net-pci,netdev=hostnet0,id=net0,    
mac=52:54:00:37:92:b2,bus=pci.0,addr=0x3 -vnc 127.0.0.1:0 -vga cirrus -device
virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5


Can anyone help sorting this out ?


Bernd

-- 
Bernd Lentes 

Systemadministration 
institute of developmental genetics 
Geb?ude 35.34 - Raum 208 
HelmholtzZentrum M?nchen 
bernd.lentes at helmholtz-muenchen.de 
phone: +49 (0)89 3187 1241 
fax: +49 (0)89 3187 2294 

Wer Visionen hat soll zum Hausarzt gehen 
Helmut Schmidt
 

Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
85764 Neuherberg
www.helmholtz-muenchen.de
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Dr. Alfons Enhsen, Renate Schlusen
(komm.)
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671

On Tue, 2016-03-01 at 14:57 +0100, Lentes, Bernd wrote:
> Hi,?
>?
> i have a weird problem. I have a vm (KVM) which seems to run fine.
[...]
> As you see, the vm has one NIC. Its MAC-Address is:
'52:54:00:37:92:03'.
> I also see that MAC when i edit the config via virsh.
>?
> But when i boot that vm, it has a nic with another MAC:
'52:54:00:37:92:B2' ???
Looks like the domain configuration has been changed while it
was already running: the inactive configuration contains the
new MAC address, but the live configuration still contains the
previous value.

Example:

? $ sudo virsh dumpxml test | grep '<mac'
????????<mac address='52:54:00:e9:0a:e1'/>

? $ sudo virsh dumpxml --inactive test | grep '<mac'
????????<mac address='52:54:00:e9:0a:5f'/>

Destroying the domain and starting it up again should be
enough for it to pick up the new MAC address.

Cheers.


PS: You should never look at the on-disk domain XML directly as
????it's owned by the deamon; always use 'virsh edit', 'virsh
????dumpxml' etc. to inspect and modify it.
--?
Andrea Bolognani
Software Engineer - Virtualization Team

On 01.03.2016 14:57, Lentes, Bernd wrote:
> Hi, 
> 
> i have a weird problem. I have a vm (KVM) which seems to run fine. I
believe the respective config file for this vm is /etc/libvirt/qemu/MausDB.xml.
This is it:
> 
> ========================================================> <domain
type='kvm'>
>   <name>MausDB</name>
>   <uuid>d4c7956c-b57f-967a-0454-99835a3a740b</uuid>
>   <memory unit='KiB'>2353792</memory>
>   <currentMemory unit='KiB'>2353792</currentMemory>
>   <vcpu placement='static'>2</vcpu>
>   <os>
>     <type arch='x86_64'
machine='pc-i440fx-1.4'>hvm</type>
>     <boot dev='hd'/>
>   </os>
>   <features>
>     <acpi/>
>     <apic/>
>     <pae/>
>   </features>
>   <clock offset='utc'/>
>   <on_poweroff>destroy</on_poweroff>
>   <on_reboot>restart</on_reboot>
>   <on_crash>destroy</on_crash>
>   <devices>
>     <emulator>/usr/bin/qemu-kvm</emulator>
>     <disk type='file' device='disk'>
>       <driver name='qemu' type='raw'/>
>       <source file='/var/lib/kvm/images/MausDB/disk0.raw'/>
>       <target dev='vda' bus='virtio'/>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x04' function='0x0'/>
>     </disk>
>     <disk type='file' device='cdrom'>
>       <driver name='qemu' type='raw'/>
>       <target dev='hda' bus='ide'/>
>       <readonly/>
>       <address type='drive' controller='0'
bus='0' target='0' unit='0'/>
>     </disk>
>     <controller type='usb' index='0'>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x01' function='0x2'/>
>     </controller>
>     <controller type='pci' index='0'
model='pci-root'/>
>     <controller type='ide' index='0'>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x01' function='0x1'/>
>     </controller>
>     <interface type='bridge'>
>       <mac address='52:54:00:37:92:03'/>
>       <source bridge='br0'/>
>       <model type='virtio'/>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x03' function='0x0'/>
>     </interface>
>     <input type='mouse' bus='ps2'/>
>     <input type='keyboard' bus='ps2'/>
>     <graphics type='vnc' port='-1'
autoport='yes'/>
>     <video>
>       <model type='cirrus' vram='9216'
heads='1'/>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x02' function='0x0'/>
>     </video>
>     <memballoon model='virtio'>
>       <address type='pci' domain='0x0000'
bus='0x00' slot='0x05' function='0x0'/>
>     </memballoon>
>   </devices>
> </domain>
> ============================================================> 
> As you see, the vm has one NIC. Its MAC-Address is:
'52:54:00:37:92:03'.
> I also see that MAC when i edit the config via virsh.
> 
> But when i boot that vm, it has a nic with another MAC:
'52:54:00:37:92:B2' ??? lspci shows me just one nic in the vm.
> This MAC-Address is also visible in the Virtual Machine Manager.
> Pictures you find here:
https://hmgubox.helmholtz-muenchen.de:8001/d/51feb02c02/
> I thought the xml-file in /etc/libvirt/qemu ist the only responsable one.
It is that one which is configured when i issue a 'edit domain' in
virsh. Or ?
Yes, it's the only location where libvirt keeps inactive domain
configurations. However, in some cases domain configuration can be fed
in from a different source, e.g. when restoring from a file. Moreover,
if the file is managed by libvirt (so called managed save), doing 'virsh
start' will run domain from there rather than from a fresh config kept
under /etc/libvirt/qemu. You can check whether domain has a managed save
by inspecting 'virsh dominfo' output.
Or if you restore a domain from previously saved state use 'virsh
save-image-edit' to check MAC address.
> Where does the VMM stores the configuration of the domains ?
Nowhere. It relies on libvirt.
> I found another xml: /var/run/libvirt/qemu/MausDB.xml . Inside it there is
the MAC the booted vm has. What is the purpose of this xml ?
It's purpose is to keep runtime configuration, libvirt's internal state
of domain, so that when libvirtd is restarted it can reload the internal
state from there.

And as Andrea already pointed out, you should never ever go behind
libvirt's back and hand edit those files. Use libvirt APIs for that
(from this POV virsh is considered as API too).

Michal

----- On Mar 1, 2016, at 5:27 PM, Michal Privoznik mprivozn@redhat.com wrote:
> On 01.03.2016 14:57, Lentes, Bernd wrote:
>> Hi,
>> 
>> Pictures you find here:
https://hmgubox.helmholtz-muenchen.de:8001/d/51feb02c02/
>> I thought the xml-file in /etc/libvirt/qemu ist the only responsable
one. It is
>> that one which is configured when i issue a 'edit domain' in
virsh. Or ?
> 
> Yes, it's the only location where libvirt keeps inactive domain
> configurations. However, in some cases domain configuration can be fed
> in from a different source, e.g. when restoring from a file. Moreover,
> if the file is managed by libvirt (so called managed save), doing
'virsh
> start' will run domain from there rather than from a fresh config kept
> under /etc/libvirt/qemu. You can check whether domain has a managed save
> by inspecting 'virsh dominfo' output.
> Or if you restore a domain from previously saved state use 'virsh
> save-image-edit' to check MAC address.
> 
>> Where does the VMM stores the configuration of the domains ?
> 
Hi,thanks for the information. I have some other questions:
what is the right way to copy (clone) a vm ? I have one vm which i want to use a
second time, on the same host, just with another MAC-Address.

And how can i copy a vm to a plain partition (without fs) ? I read this is
faster than having an image file on a file system.

Bernd
 

Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
85764 Neuherberg
www.helmholtz-muenchen.de
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Dr. Alfons Enhsen, Renate Schlusen
(komm.)
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671