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

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

[Tomasz Chmielewski]

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?


-- 
Tomasz Chmielewski
http://wpkg.org

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

[Avi Kivity]

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.



-- 
error compiling committee.c: too many arguments to function


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

[Tomasz Chmielewski]

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

[Avi Kivity]

Tomasz Chmielewski wrote:
>>
>> 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":

The various device options are documented under '-serial'.

>
>
> 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?
>
>

http://libvirt.org/

-- 
error compiling committee.c: too many arguments to function


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

[Dor Laor]

>>
>> 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
>>

You can also try with a tcp device and telnet it.

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

[Anthony Liguori]

Avi Kivity wrote:
> 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.
>   

A nice trick is to redirect the monitor to a unix socket and then use:

echo 'migrate ssh://foo' | socat stdio unix:/path/to/socket

It's pretty easy to write a small program that lets you execute monitor 
commands externally.  I've got a patch in my queue that adds a standard 
convention for monitor socket paths based on a guest "name" with the 
idea that you could write something very similar to xm.  Just have to 
figure out how to address some of the lingering issues with it (mostly, 
how to clean things up reliably on exit).

Regards,

Anthony Liguori

Regards,

Anthony Liguori

>
>   


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