Dear Friends,
I would ask you a question ; grateful in advance!
I have a program running on a VM guest. Its output is valuable (for VM
introspection) so I want to let the host module know about it. I prefer to
redirect ' stdio" of a guest into a device at the host (a text file or
my device that has the name "mydev"
and the driver is written for it).
I have the XML definition file for my VM in /etc/libvirt/qemu. I have added the
section:
<serial type="file">
<source path="/var/log/vm/vml.log"/>
<target port="0"/>
</serial>
into the /devices section.
That is I want the stdio to be streamed into the file /var/log/vm/vml.log at the
host.
Then I run simple textual commands at the guest (ls, pwd and so on). But I do
not see /var/log/vm/vml.log created at the host.
Please help me.
Thanks in advance,
Alexander Binun
>
> The command string for qemu will look like qemu -serial /dev/mydev ... But
I would like to
> modify the libvirt definition XML file (in /etc/libvirt/qemu). Stefan notes
in his blog
>
(http://blog.vmsplice.net/2011/04/how-to-pass-qemu-command-line-options.html)
that the options will
> look like:
---------- Forwarded message ----------
Date: Wed, 28 May 2014 18:06:10 +0300
From: Eric Blake <eblake@redhat.com>
To: Alexander Binun <binun@cs.bgu.ac.il>
Cc: Stefan Hajnoczi <stefanha@gmail.com>
yagel@cs.bgu.ac.il
kahilm@post.bgu.ac.il
qemu-devel@nongnu.org
boaz.menuhin@gmail.com
Paolo Bonzini <pbonzini@redhat.com>
markbl@post.bgu.ac.il
Subject: Re: excuse me for incorrect question...
On 05/28/2014 08:43 AM, Alexander Binun wrote:> Eric, I aplogize for making your work complicated.
[You top-posted again]
No need to apologize - these lists exist to help people, and we were all
new once.
>
> Should I send questions to libvirt-users@redhat.com instead ? I would ask
more questions.
Yes, if your questions are related to libvirt, then asking on a libvirt
list will get you a better audience that may have better answers to your
questions.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
On 05/28/2014 08:43 AM, Alexander Binun wrote:> Eric, I aplogize for making your work complicated.
[You top-posted again]
No need to apologize - these lists exist to help people, and we were all
new once.
>
> Should I send questions to libvirt-users@redhat.com instead ? I would ask
more questions.
Yes, if your questions are related to libvirt, then asking on a libvirt
list will get you a better audience that may have better answers to your
questions.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
On 05/28/2014 09:14 AM, Alexander Binun wrote: [can you convince your mailer to wrap long lines?]> > I have a program running on a VM guest. Its output is valuable (for VM introspection) so I want to let the host module know about it. I prefer to redirect ' stdio" of a guest into a device at the host (a text file or my device that has the name "mydev" > and the driver is written for it). > > I have the XML definition file for my VM in /etc/libvirt/qemu. I have added the section: > > <serial type="file"> > <source path="/var/log/vm/vml.log"/> > <target port="0"/> > </serial> > > into the /devices section. > > That is I want the stdio to be streamed into the file /var/log/vm/vml.log at the host. > > Then I run simple textual commands at the guest (ls, pwd and so on).How are you getting into your guest to run those commands? Did you connect to your guest's serial console, or is it in a gui window, or via an ssh session, or...? Are you sure the commands you are executing have the guest's /dev/ttyS0 as their stdout?> But I do not see /var/log/vm/vml.log created at the host.I'm not sure whether libvirt will pre-create the file, or whether it insists that the file already exists. Maybe others can chime in. I know Dave Allan has done some work with python scripts that faithfully capture all text output to the guest's serial console, although I don't have a handy link to that sample script. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
On Wed, May 28, 2014 at 11:28:19AM -0600, Eric Blake wrote:> On 05/28/2014 09:14 AM, Alexander Binun wrote: > > [can you convince your mailer to wrap long lines?] > > > > > I have a program running on a VM guest. Its output is valuable (for VM introspection) so I want to let the host module know about it. I prefer to redirect ' stdio" of a guest into a device at the host (a text file or my device that has the name "mydev" > > and the driver is written for it). > > > > I have the XML definition file for my VM in /etc/libvirt/qemu. I have added the section: > > > > <serial type="file"> > > <source path="/var/log/vm/vml.log"/> > > <target port="0"/> > > </serial> > > > > into the /devices section. > > > > That is I want the stdio to be streamed into the file /var/log/vm/vml.log at the host. > > > > Then I run simple textual commands at the guest (ls, pwd and so on). > > How are you getting into your guest to run those commands? Did you > connect to your guest's serial console, or is it in a gui window, or via > an ssh session, or...? Are you sure the commands you are executing have > the guest's /dev/ttyS0 as their stdout?Your xml is correct and I think Eric's suggestion is right: if I put that <serial> snippet into a guest's XML and then echo "foo" > /dev/ttyS0 in the guest, I see "foo" in the host vml.log.> > But I do not see /var/log/vm/vml.log created at the host. > > I'm not sure whether libvirt will pre-create the file, or whether it > insists that the file already exists. Maybe others can chime in. I know > Dave Allan has done some work with python scripts that faithfully > capture all text output to the guest's serial console, although I don't > have a handy link to that sample script.The example script is consolecallback.py[1] but it really deals more with auto connecting to a serial console when a VM is booted than with doing anything special with the output, although it's useful if you have a VM going up and down and you want all its console output. Dave [1] http://libvirt.org/git/?p=libvirt-python.git;a=blob;f=examples/consolecallback.py;hb=HEAD> -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org >
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