Primary / Secundary cluster with synced leases created using omapi

Glenn Satchell glenn.satchell at
Sun Aug 7 15:08:57 UTC 2016

Hi Matt

If you are running failover, then the dhcpd.leases files on each system
are not the same. It records information about the state of the partner's
leases and it's own leases with different flags. If you search through the
file on each system looking for a lease for the same IP address you can
see what I mean.

There is more info in the dhcpd.leases man page, although most of the
discussion is about the file format.


On Sun, August 7, 2016 11:58 pm, Matt . wrote:
> OK, this clears it out.
> Why would it not be possible to sync the leases file then ? Or is
> there some other database style file which going to be corrupted or is
> it that the running process doesn't know the synced data on the host
> which hasn't have it added through omapi ?
> 2016-08-07 14:18 GMT+02:00 Glenn Satchell <glenn.satchell at>:
>> This style of host declaration creates a static lease. If it set in
>> dhcpd.conf it does not generate an entry in the leases file, and it is
>> not
>> handled by the failover protocol.
>> In your case, if you add the entry via omapi, then you need to do the
>> same
>> operation to the second dhcp server.
>> The equivalent would be defining the host declarations in the dhcpd.conf
>> on both dhcp servers.
>> regards,
>> -glenn
>> On Sun, August 7, 2016 10:05 pm, Matt . wrote:
>>> What I mean by static leases is:
>>> host myhostname {
>>>  hardware ethernet 00:20:00:2c:5b:7a;
>>>  fixed-address;
>>> }
>>> That is what I cannot do, but is no issue if the added leases my
>>> omapi, so reserved flag as you call them, are synched to the secondary
>>> server, and that is not happening it seems.
>>> I need to know if it doesn't happen at all and it's not the way how
>>> it's designed or something is just not working here.
>>> 2016-08-07 13:44 GMT+02:00 Simon Hobson <dhcp1 at>:
>>>> Matt . <yamakasi.014 at> wrote:
>>>>> I'm having an issue with a setup where I can't set static leases.
>>>> Define what you mean by static leases.
>>>> Do you mean a host statement with a "fixed address" statement, or a
>>>> lease with the reserved flag set ?
>>>> I assume you mean the former, and that means that what you are setting
>>>> isn't a "lease" in the conventional sense - host statements with fixed
>>>> address do not create a lease through the normal lifetime. Normally
>>>> these do not appear in the leases file at all, and I suspect that they
>>>> do not get processed by failover either.
>>>> I'm assuming that they appear in the leases file when created via
>>>> OMAPI
>>>> as otherwise there would be no persistent storage of them.
>>>> So in this case, you need to apply the change to both servers.
>>>> Or, use reserved leases and failover which should work.
>>>> BTW - syncing the leases file is "fraught with difficulties" and is
>>>> guaranteed to break things unless you use nothing but these static
>>>> leases. The server you sync the file *to* will ignore it unless you
>>>> stop
>>>> the dhcpd service, swap out the file, and start the dhcpd service.
>>>> This
>>>> is because the leases file is "write only" - it is read once at
>>>> service
>>>> startup, and then it is only written (so there's persistent storage) -
>>>> all the working data is held in ram.
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