6:16 a.m.
I'm a Libvirt newbie and I'd really appreciate it if someone could answer
my doubts. I'm using Libvirt's Java API.
My doubts:
1.Currently, I'm able to create a VM on Ubuntu 11.04 using Libvirt
functions domainCreateLinux() and domainDefineXML(). Apart fromt the
boolean return status of these operations and running the virsh list
command, is there any way to SSH in (login) to the newly created VMs and
run applications on them? I tried running virsh console but nothing comes
up. Also I tried fixing the XML file to accommodate the console operation(
link <http://ubuntuforums.org/showthread.php?t=1159220>) but that was
unsuccessful too.
2. If yes, how can I get the IP of the VM created?
3. Is there any function to create image files(in any format qcow or qcow2)
using Libvirt API? Right now, I'm using a shell script which creates the
image from it's iso.
Thanks in advance
P Ramesh
8:28 a.m.
Am 16.11.2011 14:46, schrieb William A. Mahaffey III:
The route command on the host will show the newly added routes for
the
VM. Also, tail your syslog file & you will see messages about every 15
min. from dnsmasq w/ the IP adder. of the VM.
route just shows the bridge, the individual IP of the VM is only shown
in the syslog. However, this is just a workaround, and does not provide
reliable identification of the IP if there are many VMs. libvirt resp.
virsh should provide a way of obtaining the IP directly from the domain
name.
Best, Till
--
Prof. Dr. Till Mossakowski Cartesium, room 2.51 Phone +49-421-218-64226
DFKI GmbH Bremen Fax +49-421-218-9864226
Cyber-Physical Systems Till.Mossakowski(a)dfki.de
Enrique-Schmidt-Str. 5, D-28359 Bremen http://www.dfki.de/sks/till
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Trippstadter Str. 122, D-67663 Kaiserslautern
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supervisory board: Prof. Hans A. Aukes (chair)
Amtsgericht Kaiserslautern, HRB 2313
9:46 a.m.
On 11/16/11 08:28, Till Mossakowski wrote:
Am 16.11.2011 14:46, schrieb William A. Mahaffey III:
> The route command on the host will show the newly added routes for the
> VM. Also, tail your syslog file & you will see messages about every 15
> min. from dnsmasq w/ the IP adder. of the VM.
route just shows the bridge, the individual IP of the VM is only shown
in the syslog. However, this is just a workaround, and does not
provide reliable identification of the IP if there are many VMs.
libvirt resp. virsh should provide a way of obtaining the IP directly
from the domain name.
Best, Till
output from 'route -CFvnee' as root on my host attached, 4th line in
file shows IP addr of my VM, visible in other lines as well ....
& I definitely agree that virsh *should* show that info :-) ....
--
William A. Mahaffey III
----------------------------------------------------------------------
"The M1 Garand is without doubt the finest implement of war
ever devised by man."
-- Gen. George S. Patton Jr.
10:01 a.m.
On 16.11.2011 16:46, William A. Mahaffey III wrote:
On 11/16/11 08:28, Till Mossakowski wrote:
> Am 16.11.2011 14:46, schrieb William A. Mahaffey III:
>
>> The route command on the host will show the newly added routes for the
>> VM. Also, tail your syslog file & you will see messages about every 15
>> min. from dnsmasq w/ the IP adder. of the VM.
>
> route just shows the bridge, the individual IP of the VM is only shown
> in the syslog. However, this is just a workaround, and does not
> provide reliable identification of the IP if there are many VMs.
> libvirt resp. virsh should provide a way of obtaining the IP directly
> from the domain name.
>
> Best, Till
>
>
output from 'route -CFvnee' as root on my host attached, 4th line in
file shows IP addr of my VM, visible in other lines as well ....
& I definitely agree that virsh *should* show that info :-) ....
It is not so simple. Although we have this 'ip address learning module'
in nwfilters code, it is not reliable. In general there is no reliable
technique to determine guest IP address(es) unless using guest agent
who'll tell us.
Listening on bridge and guessing addresses is not right, as guest might
be not playing a fair game and produce packets with different IP addresses.
Moreover, sniffing on multiple bridges and guessing IP addresses can be
CPU consuming. And one would need to do this sniffing repeatedly as IP
address might change over time.
Michal
10:09 a.m.
On 11/16/2011 08:46 AM, William A. Mahaffey III wrote:
>> The route command on the host will show the newly added
routes for the
>> VM. Also, tail your syslog file & you will see messages about every 15
>> min. from dnsmasq w/ the IP adder. of the VM.
>
& I definitely agree that virsh *should* show that info :-) ....
This has been an oft-requested feature, but no one has yet submitted
patches. The closest we have is that use of nwfilter can snoop a
guest's address, but this isn't yet exposed to the user via an
easy-to-access API. If you set up a DHCP server to assign guest IP
addresses based on guest MAC address, then you know what IP address the
guest should have. But if this is not the case, then the only way
libvirt can learn this is by snooping - libvirt can snoop DHCP traffic
to learn what an external dhcp server is giving to the guest, as well as
snoop guest traffic to see what address the guest appears to be using.
But a malicious guest can spoof this snooping, not to mention that a
guest that uses multiple IP addresses on a single interface may confuse
libvirt, which will probably only snoop the first address used. And a
guest that never initiates traffic is hard to snoop - making it hard to
know what address to use for ssh into the guest. There are also plans
to make use of a guest agent for communicating the guest IP address back
over the agent channel (right now, libvirt's only use of a guest agent
is for triggering guest shutdown), but again this relies on the agent
being present in the guest and cannot be deemed 100% reliable.
Use of libvirt guest console features tends to be more reliable than
trying to ssh into a guest, since that bypasses the need to learn the
guest's IP address.
--
Eric Blake eblake(a)redhat.com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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5 comments
5 participants
participants (5)
-
Eric Blake -
Michal Privoznik -
Preethi Ramesh -
Till Mossakowski -
William A. Mahaffey III