Re: scripted migration (without Alt-Ctrl-2 / qemu-monitor) - possible?

[Tomasz Chmielewski <mangoo-Nem3ZqsbT/g@public.gmane.org>]

Avi Kivity schrieb:
> Tomasz Chmielewski wrote:
>> Is it possible to do a migration (or any other maintenance, like 
>> stopping a guest VM) without qemu-monitor / Alt-Ctrl-2?
>>
>>
>> For those using Xen, it would be similar to a command line "xm" which 
>> migrates a guest/domain to a different host - just SSH to your server 
>> (or use it in a script etc.), and do:
>>
>> xm migrate <Domain> <Host>
>>
>>
>> Similarly, lots of other actions are possible, like pausing, 
>> rebooting, shutting down, saving, restoring etc.
>>
>>
>> The idea of having to "alt-ctrl-2 on the SDL window" does seem a bit 
>> incompatible with CLI, doesn't it?
>>
>>   
> 
> Look up the qemu -monitor option.  This allows you to redirect the qemu 
> console anywhere you like, including stdio, pipes, tcp sockets, etc.  
> It's wonderfully flexible.

All right - so I see it belongs more to qemu documentation than KVM's 
(+/- KVM extensions like migration etc.).


Not as easy to use and intuitive as "xm" - some instruction here, as 
Qemu's "-monitor dev" documentation seems a bit incomplete as it 
mentions only "vc" and "stdio":


1. Make a /tmp/guest socket; then start a guest

qemu (...) -monitor unix:/tmp/quest,server,nowait


2. Show qemu-monitor's help:

echo 'help' | socat - unix-connect:/tmp/quest


The things get more complicated if you run multiple quests - you have to 
keep track of the pipes etc.


Certainly, it is possible to write a powerful backend to that - as you 
say, if it supports tcp sockets, it would be even possible to support 
multiple KVM/qemu servers with one program or a script - something that 
Xen's "xm" can't easily do.


Are there any ready solutions for that? Or the wheel still waits to be 
invented?


-- 
Tomasz Chmielewski
http://wpkg.org


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