upgrading

[Glenn Satchell]

>Date: Thu, 4 Oct 2007 15:15:24 +0100
>To: dhcp-users at isc.org
>From: Simon Hobson <dhcp1 at thehobsons.co.uk>
>Subject: Re: upgrading
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>
>Glenn Satchell wrote:
>
>>  >We're running 3.0.1 here and feel it's time to upgrade. We have seen some
>>>weird no free leases errors that have caused some problems for us and are
>>>hoping an upgrade may help.
>>>
>>>We are running two servers in peer mode and want to upgrade both servers. I
>>>believe we're upgrading to 3.0.6
>>>
>>>I'm just wondering what the upgrade path should be since we are running the
>>>two servers in peer mode. Should we upgrade them at the same time? Can they
>>>run in peer mode at different code levels?
>
>
>
>>Make a copy of dhcpd.leases on each system in case you need to roll
>>back.
>>
>>You should run the same version on both dhcp servers if you're using
>>failover. So shutdown both, uninstall the existing package on each,
>>install the new package on each, start them up one after the other.
>
>
>That's potentially a significant period with no DHCP service. Am I 
>right in thinking that an alternative could be to :
>
>- shut down the primary and put the secondary in partner down mode
>- upgrade the primary and test the config
>- shut down the secondary, copy the leases file to primary, start up 
>the primary & put it in partner down mode
>- upgrade secondary, clear it's leases file, and start it
>
>Slightly more work, but only a short interruption in service.
>
Well, yeah, you could do that, except for the bit about copying leases
files to the other host. The system will synchronise those itself when
it starts.

I was thinking that this would be a job done in a quiet period, and if
you had things ready before shutting anything down would be about 10
minutes outage. My preferred time was about 11 am as the morning rush
is over and you can then watch it for the afternoon to make sure it is
handing out addresses ok, but of course YMMV.

Remember this is only an outage to new hosts trying to gain an address.
Anything renewing will just try again until it succeeds. Hosts trying
to renew won't gain any benefit from the partner down as they unicast
back to the host that initially gave them the address - they don't know
about the peer and can't ask it to renew their lease.

regards,
-glenn