[Dnsmasq-discuss] dnsmasq 2.91 DUID in leases file format

[Simon Kelley]

The lease file format isn't documented because it isn't public. There 
are no promises to keep it backwards compatible beyond best-effort to 
avoid breaking older versions of dnsmasq itself with new changes.

The duid line just holds the UID for the server which is used when the 
server does DHCP for IPv6. If DHCPv6 is actually in use, it will be 
followed by DHCPv6 leases which also have a different format to the 
DHCPv4 leases you're seeing.

For completeness, the current development version of dnsmasq may also 
store lines that start "vendorclass" if the DHCP leasequery facility is 
enabled.




Cheers, Simon



On 01/07/2025 08:07, Gino McCarty via Dnsmasq-discuss wrote:
> Hello, having trouble sourcing documentation, on this leasing file 
> format behavior and hoping you can help.
> 
> in my leases file some machines  generate the following format
> 
> ```
> 
> duid 00:01:00:01:2f:f0:f6:60:2c:cf:67:af:44:ab
> 
> ```
> 
> I can find no documentation for this syntax, normally I would ignore 
> this except it is throwing an error in Google's dnsmasq_exporter which I 
> use to generate Prometheus metrics from dnsmasq data.
> 
> See: https://github.com/google/dnsmasq_exporter/issues/33
> 
> 
> Any documentation or guidance would be helpful
> 
> Google seems unwilling to just ignore the line without additional context.
> 
> 
> Thanks,
> 
> 
> Gino
> 
> On Monday, June 30th, 2025 at 12:01 AM, Gino McCarty 
> <onigino at protonmail.com> wrote:
>>
>> Hello, having trouble sourcing documentation, on this leasing file 
>> format behavior and hoping you can help.
>>
>> in my leases file some machines  generate the following format
>>
>> ```
>>
>> duid 00:01:00:01:2f:f0:f6:60:2c:cf:67:af:44:ab
>>
>> ```
>>
>> I can find no documentation for this syntax, normally I would ignore 
>> this except it is throwing an error in Google's dnsmasq_exporter which 
>> I use to generate Prometheus metrics from dnsmasq data.
>>
>> See: https://github.com/google/dnsmasq_exporter/issues/33
>>
>>
>> Any documentation or guidance would be helpful
>>
>> Google seems unwilling to just ignore the line without additional context.
>>
>>
>> Thanks,
>>
>>
>> Gino
>>
> 
> 
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