[Lxc-users] Live Migration of LXC

[Daniel Lezcano]

Sagar Dixit wrote:
> Hi Daniel,
>
> Firstly, thanks for such a detailed response. However, I am still not clear
> on few issues.
>
> On Sat, Mar 20, 2010 at 4:30 PM, Daniel Lezcano <daniel.lezcano at free.fr>wrote:
>
>   
>> Sagar Dixit wrote:
>>
>>     
>>> Hi,
>>>
>>> I read on libvirt website that it supports LXC. Just curious to know if I
>>> can use libvirt live migration APIs with LXCs to migrate them from one
>>> machine to other ?
>>>
>>>
>>>       
>> There is a confusion the word LXC. Libvirt took this name at the same time
>> the lxc tools were developed.
>> The lxc tools are standalone userspace commands to use the containers. The
>> LXC in libvirt is coded inside, without an external component
>>     
>
> (maybe someone, one day will create a driver for the lxc tools, who knows
>   
>> ...).
>>
>>     
>
> So what does the LXC code in libvirt exactly do ?  Sorry, but I did not get
> " is coded inside, without external component"
>   

Libvirt is a glue between an uniform API to manage Virtual machines and 
specific VM implementation.
Each VM has a libvirt _driver_ implementing this glue.
But LXC is an exception where the driver is the container 
implementation, not a glue. The container is hardcoded inside the libvirt.

The lxc tools are userspace utilities, standalone, with another 
container implementation and nothing in common with the libvirt.

in other words libvirt LXC is not a driver but a container 
implementation and
libvirt LXC is not the lxc tools.

In order to use the lxc tools with libvirt, a specific glue, a driver, 
should be implemented to use them through the libvirt as there is a 
openvz driver.

>> The checkpoint / restart (aka migration, live migration, etc ...) is not
>> mainstream, so it is not implemented in the libvirt.
>>
>> There will be available a kernel patchset in a few weeks making possible to
>> do live migration with the lxc userspace tools (not libvirt), with some
>> restrictions.
>>
>> In the same time, there is another checkpoint / restart kernel patchset on
>> the way asking for mainstream inclusion and there are some patchset for lxc
>> to integrate this implementation.
>>
>> So within 2/3 months, we should have lxc with 2 checkpoint/restart
>> solutions embedded in it.
>>
>>     
>
> Is there currently, facility provided by LXC tools (userspace) to checkpoint
> and restart ?
>   
Not yet, it's on the way.