[libvirt-users] Questions on how to reset ID numbers for virt Guests.

[Eric Blake]

On 09/11/2013 01:59 AM, Daniel P. Berrange wrote:
> On Wed, Sep 11, 2013 at 09:47:07AM +0200, Paolo Bonzini wrote:
>> Il 11/09/2013 00:27, James Sparenberg ha scritto:
>>> I'm doing some experimenting in our Development lab and as a result
>>> I'm kickstarting over and over Virtual guests.  This is of course
>>> causing the guest Id to increment by one with each test.  I've
>>> googled around and tried searching the list but have not found out
>>> how (if at all) it would be possible to reset the ID number back to 1
>>> more than is in use.  Also is there  a limit where I run out of ID's?
>>> (for example does it only go up to 99?)
>>
>> No, there is no limit.
> 
> Well, 'int' will wrap eventually, but you'd need to have created
> a hell of alot of guests for that to be a problem :-)

2**31 (~2 billion), to be exact, since we store it as a signed int, and
I'm not sure if all the code paths handle a negative number gracefully
(see src/datatypes.h:_virDomain).  (Maybe we should have picked a 64-bit
type, so that wraparound would not be possible within our lifetimes even
with a process spawning guests as fast as possible on current computers
- but even with a 32-bit number, it's going to take a lot of hammering
to hit wraparound)

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

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