Nameserver Problem [more] -
Tony Nelson
tonynelson at georgeanelson.com
Tue Apr 3 15:52:37 UTC 2007
At 5:08 PM +0930 4/3/07, Tim wrote:
>Ed Greshko:
>>>> While that works, you really should be updating the serial number each
>>>> time you make a change to a zone file.
>
>Tim:
>>> Yes, but there weren't any changes being made to that zone file. So
>>> it's not needed. You'd only have to do that if you'd changed records
>>> *in* it. All we were doing is adding domains that used it.
>
>Ed Greshko:
>> I didn't mean to imply that something had changed. Just making a statement
>> about the serial number and "good practice".
>
>Only if the zone file had actually changed. It's actually *bad*
>practice to change a serial number on a zone if none of its details
>changed. It breaks caching, everything will reload it unnecessarily.
>
>In this instance, it was leading Bob astray with an unrelated issue.
>You don't change the serial number with each edit of your DNS server
>configuration, just when it's actually necessary.
>
>> While using a date format is only a recommendation it is considered by
>> many to be good practice.
>
>I've seen a few things which merely increment the serial number. Such
>as the DHCP that comes with Fedora. If you started off using dates,
>it'd just add one to the number, and you're left with a nonsense number
>in the serial code. Sure, it'll work, as it's a higher number, but it
>won't mean what you think it did.
>
>Using a date code is a simple way of putting in a new serial code
>without caring what the prior number is. But that has its own problems.
>It can make a serial code go backwards if it was already a higher
>number, because the last editor used a different scheme. It's quite
>easy for that to happen if you'd done numerous changes to a zone file in
>one day, there's not enough digits in the code to do years+months+days
>+hours+minutes+extra_changes. At least, not enough digits in some DNS
>servers that I've used.
>
> From a programatic point of view, you really need to check what the
>number was, and *at* *least* increment it by one. But *only* do so when
>needed.
For zone files which are an ultimate answer and thus will never change, a
convention is to use a serial number of "42". Don't change dead.zone now,
though! The procedure for decrementing a zone serial number is, umm,
convoluted.
--
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' <http://www.georgeanelson.com/>
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