[libvirt-users] Programmatically force shutdown a guest: possible?

[Ivan Kabaivanov]

or you could do it through an acpi event.  If you use kde, you can shut it down via dbus.  This is how I did it (as root):

su - username -c "DBUS_SESSION_BUS_ADDRESS='unix:abstract=/tmp/dbus-vS7K32zzd7,guid=9eb3fedc45f523665b178a4d53373536' qdbus-qt4 org.kde.ks
mserver /KSMServer logout 0 0 0"

In theory this should work too, if your dbus is compiled with support for X11 dbus-daemon autolaunch:

su - username -c "DISPLAY=:0 qdbus-qt4 org.kde.ksmserver /KSMServer logout 0 0 0"

The trick is to know which user is currently logged in and to know/find out their DBUS_SESSION_BUS_ADDRESS.  The former is easy:
who | awk '!/pts/ {print $1}'

This will print the username of whoever is logged into X.  If you get nothing, nobody is logged on :0 and you could use wall to prompt all currently logged in users to log out, give them a grace period of say one minute, then shutdown.  If on the other hand you have someone logged into X, you could use kdialog/zenity/xmessage to tell them they have say a minute to quit whatever they are doing, then you can use the dbus to shutdown.  It works for KDE.  I don't know if/how it works for GNOME/Unity/XFCE, etc.

As for the DBUS_SESSION_BUS_ADDRESS, if you use a standard/modern distribution this is probably available in the user's shell environment variables already, so you need not worry about it.  Trouble is it may not be available outside the X session.  You'll need to change your KDE/GNOME/XFCE, etc start-up scripts to print this variable into a file, which you can later source when you need it.

But you can control how your system will react on an acpi shutdown via the acpi hooks.  You don't have to get real fancy and worry about graceful shutdown, cause under certain conditions it may not be possible to quit your graphical environment -- I've had stubborn processes refuse to end and the shutdown is canceled.  Read the dbus documentation about the three numerical parameters (0 0 0 in this case) -- they deal with session control, etc.  Read up on acpi events as well and you should figure it out.

IvanK.





----- Original Message -----
From: "Pasquale Dir" <phate867 at gmail.com>
To: "Eric Blake" <eblake at redhat.com>
Cc: libvirt-users at redhat.com
Sent: Sunday, March 30, 2014 11:47:23 AM
Subject: Re: [libvirt-users] Programmatically force shutdown a guest:	possible?

Yes, you are right. 
Listen, as the documentation is not very exaustive, can you explain briefly to me how a guest agent works? 
After installing it via the apt-get on the hypervisor (I am using ubuntu as host system) how can I create a script which would do this? 
That is waiting for an acpi signal and actually shut down the guest. 

And what other operation can you actually do with a guest agent? I would be interested in getting the current amount of memory the guest is using too...as libvirt apis just tell me the max memory allocated. 


2014-03-29 15:12 GMT+01:00 Eric Blake < eblake at redhat.com > : 



On 03/29/2014 06:21 AM, Pasquale Dir wrote: 
> I am looking at the shutdown method, but if the guest system is a desktop 
> system, like for example ubuntu, it just has the effect to show a box 
> prompting the user for a shutdown/reboot/ and such. 
> 
> I could enter the guest and change this default behaviour and it actually 
> works..but I'd like for a way to send a shutdown command without doing so. 
> 
> Is it possible? 

Guest shutdown is ALWAYS a cooperative action. It sounds like your 
guest defaults to an interactive shutdown when an ACPI shutdown request 
is received. You can install qemu-guest-agent in your guest and send 
shutdown via the agent instead of via ACPI - that may be a bit more 
responsive at doing an immediate shutdown. But beyond that, no, there 
is no way to guarantee a graceful guest shutdown without guest 
cooperation. If you must stop a guest, and shutdown is taking too long 
because the guest is not cooperating, then use the 'virsh destroy' command. 

-- 
Eric Blake eblake redhat com +1-919-301-3266 
Libvirt virtualization library http://libvirt.org 



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