Changing $TTL for many zones

[Barry Margolin]

In article <celmca$1u4a$1 at sf1.isc.org>,
 Josh Harding <jharding at brave.cs.uml.edu> wrote:

> I was wondering if it's possible to use an include with bind9 to set the 
> time to live. This would allow me to easily change the ttl when we make 
> changes in the future. The syntax I was contemplating would look like this
> in db.somedomain:

It would make things easy when you make a change that impacts all your 
zones.  But how often do you make those kinds of changes, compared with 
single-zone changes?

>  $include db.ttl.inc
> 
> and in db.ttl.inc:
> $TTL 86400      ;to be changed at my convenience
> 
> Would this work?

One negative implication is that when you do "ndc reload", it always 
rereads any zone files that contain $INCLUDE -- other zone files are 
only reread if their modification time is newer than it was the last 
time it was read.  This is because BIND doesn't record of all the 
$INCLUDE files that were involved in loading a zone, so it can't check 
whether any of them have updated; if any $INCLUDEs were used, it just 
assumes the worst and reloads it.  If you're hosting lots of zones 
(which I assume you are because you're looking for this type of 
convenience), this could make reload times significantly longer.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***