Update procedure

[David Coulthart]

On Mar 26, 2009, at 5:33 PM, David W. Hankins wrote:
> On Thu, Mar 26, 2009 at 04:18:36PM -0400, David Coulthart wrote:
>> What would the update procedure look like if you need to do an  
>> upgrade from
>> 3.0.x to 4.1.x?  If I upgrade one server to 4.1.x without taking  
>> down the
>> second one still running 3.0.x (so I don't cause an outage for my  
>> users)
>> will dhcpd recognize that they're trying to speak incompatible  
>> versions of
>> the failover protocol and just refuse to talk to one another?  Or  
>> could
>> this result in some form of lease file corruption so I have to take  
>> both
>> servers down before bringing them up on 4.1.x (causing a brief  
>> outage for
>> users)?
>
> There's no risk to the lease database.  Older versions would log very
> odd looking errors, newer versions more gently explain the problem.
>
> I usually recommend faulting the lease database with the 3.0->3.1+
> upgrade (because a lot of bugs throughout development would cause
> lease database inconsistency) "just to be sure," but that's up to you.

Based on this message:

https://lists.isc.org/pipermail/dhcp-users/2008-September/007051.html

faulting the lease database seems to mean moving the existing  
dhcpd.leases file out of the way and allowing it to re-sync using the  
failover protocol.

Are you suggesting the same thing as you did in that message -- to  
fault just the secondary's database?  So the procedure to upgrade  
would look something like:

1) Stop old dhcpd on primary (secondary continues answering users)
2) Start new dhcpd on primary w/existing dhcpd.leases (no failover  
sync will take place b/c of protocol mismatch)
3) Stop old dhcpd on secondary
4) Move dhcpd.leases on secondary out of the way
5) Start up new dhcpd on secondary w/empty dhcpd.leases (relying on  
failover to sync w/primary)

If this is what you are suggesting, won't that mean that any leases  
given out by the secondary b/w steps 1 & 3 are lost?  If planned  
properly the time b/w steps 1 & 3 should be minimal, but I just want  
to make sure I'm understanding the full picture.

Thanks,
Dave Coulthart