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Re: [virt-tools-list] how to reboot virtual machine / guest OS??

On 11/10/2010 07:22 AM, Santanu Das wrote:
Hi there,

How can I reboot the virtual guest after creating it? I'm gonna use PXE/Kickstart method to install the OS, os a reboot is needed for the PXE to pick up the information. I I try to reboot the virtual machine from the virt-manager interface, I get this error:

    Error shutting down domain: this function is not supported by the hypervisor: virDomainReboot

    Traceback (most recent call last):
       File "/usr/share/virt-manager/virtManager/engine.py", line 531, in reboot_domain
       File "/usr/share/virt-manager/virtManager/domain.py", line 565, in reboot
       File "/usr/lib64/python2.4/site-packages/libvirt.py", line 392, in reboot
         if ret == -1: raise libvirtError ('virDomainReboot() failed', dom=self)
    libvirtError: this function is not supported by the hypervisor: virDomainReboot

So, is it not possible?

Not really possible from libvirt.

Please consider that there is not, and has never been, a reboot button on any intel based hardware I have ever seen. There is no reboot method described by the ATX motherboard (nor any others that I am aware of) nor does (or can) APIC.

There is no way for libvirt to send a 'reboot' to a VM that could possibly be reliable since there is no hardware support for it.

Also consider that Windows (XP, 2k3) does not even respond to the APIC/ATX 'power' button press unless a user is logged in. Windows 2k8r2 does see the signal, but ignores it unless a user is logged in, or unless a second press is received within a few seconds.

Therefore, there cannot be a reliable way for libvirt to gracefully shutdown a VM.

However, virsh destroy is reasonably reliable as it simply kills the VM process on the host. But this is obviously not a recommended way of shutting down systems.

VM users need to be responsible for 'rebooting' their systems, or you need to force a user login on Widows VMs (not recommended)

A great deal of work has gone into the libvirt tools such as virt-install to allow reboots during installs. There are many 'definitions' for various flavors of operating systems that describe to virt-install how to handle things. For instance: Windows 2k8r2 needs TWO reboots to complete the install. Thus, you must pass --os-type=win2k8 to virt-install so it knows to allow that.

The discussion of libvirt reboots is not over, but for now, its not really possible.

Good Luck!

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