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Every time I boot my system (usually every 2-3 days)
I automatically download the official "named.root" file
that lists the top-level name servers to check for any
changes"
to check for changes I do a diff on the new file against
the previously downloaded file. Usually, there are no
differences, but on occasion, although the root servers
are unchanged, the file indicates an update.
Why? That is, why indicate an update when no changes
have occurred?
I show the diff file from the latest "update." Only
the date has changed. Everything else is the same.
Systemd free - always and forever
D.E. free - always and forever
Grant Taylor
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Oct 23, 2020, 7:13:36 PM10/23/20
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On 10/23/20 4:32 PM, F Russell wrote:
> Every time I boot my system (usually every 2-3 days) I automatically
> download the official "named.root" file that lists the top-level name
> servers to check for any changes"
Why do you do this?
You should only need knowledge of one functional root server to populate
the list of the rest of them. So if one, or even a few, are at
different addresses, it won't cause a problem.
> to check for changes I do a diff on the new file against the previously
> downloaded file. Usually, there are no differences, but on occasion,
> although the root servers are unchanged, the file indicates an update.
>
> Why? That is, why indicate an update when no changes have occurred?
If I'm interpreting the following lines correctly, I'm guessing that the
root zone itself changed, and that caused the process that automatically
generates the named.root file to be updated.
> ; last update: October 22, 2020 | ; last update: September 14, 2020
> ; related version of root zone: 2020102201 | ; related version of root zone: 2020091401
> I show the diff file from the latest "update." Only the date has
> changed. Everything else is the same.
The date of the named.root file would naturally change if the named.root
file is updated to match the root zone version.
--
Grant. . . .
unix || die
F Russell
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Oct 23, 2020, 8:09:52 PM10/23/20
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On Fri, 23 Oct 2020 17:13:44 -0600, Grant Taylor wrote:
Pdnsd allows caching as well for faster subsequent lookups,
as well as filtering based on the "hosts" file.
>
> If I'm interpreting the following lines correctly, I'm guessing that the
> root zone itself changed,
> The date of the named.root file would naturally change if the named.root
> file is updated to match the root zone version.
What exactly is the "root zone?"
But that would represent the only difference.
All of this is totally inconsequential. I am just curious why
the file would indicate an update even though no root server
address has changed.
Grant Taylor
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Oct 23, 2020, 8:21:57 PM10/23/20
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On 10/23/20 6:09 PM, F Russell wrote:
> Because I use pdnsd to bypass my ISP nameserver:
>
> http://members.home.nl/p.a.rombouts/pdnsd/index.html >
> Pdnsd allows caching as well for faster subsequent lookups, as well
> as filtering based on the "hosts" file.
I get running a local recursive resolver. I've been doing it for the
better part of two decades.
But if you already have a file that is -- let's say -- > 90% accurate,
given the way that resolvers work, why do you need to (re)download the
file every time you boot?
I could definitely see monthly, or /maybe/ even weekly. But I don't see
why do it on every boot.
Also, depending on how you're downloading it, there's a good chance that
you can enhance the download so that it only does so if the file on the
server changes on the remote server.
> What exactly is the "root zone?"
It's the zone that actually contains the information that you talk to
the root servers to get.
> But that would represent the only difference.
>
> All of this is totally inconsequential. I am just curious why the
> file would indicate an update even though no root server address
> has changed.
The named.root file is effectively a very small ancillary piece of DNS.
As such, it's trivial to update it if / when other parts of the DNS root
change.
Think about it this way. You tell make to rebuild files (like
named.root) any time other source files (like the root zone) is updated.
It doesn't matter if the contents that go in the target file
(named.root) change or not. The process causes a new target file to be
created.
So when the root zone file is updated (new TLD, or existing TLD
nameserver changes, or DNSSEC data changes) the associated named.root
file will /also/ be updated. It's a cascading effect, even if the
contents of the named.root file doesn't substantially change.
F Russell
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Oct 23, 2020, 8:30:53 PM10/23/20
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On Fri, 23 Oct 2020 18:22:03 -0600, Grant Taylor wrote:
>
> I could definitely see monthly, or /maybe/ even weekly. But I don't see
> why do it on every boot.
>
Why not?
The addresses of the root servers did change on occasion
in the past, and I would change my pdnsd config file
in response.
But I have not seen any change in a root server address
in years and I am just wondering why they would indicate
just a change in date.
Grant Taylor
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Oct 23, 2020, 8:48:33 PM10/23/20
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On 10/23/20 6:30 PM, F Russell wrote:
> Why not?
Because it doesn't change that often.
Because it's some additional load.
Because it's not necessary load.
Because the way that recursive DNS servers operate, only one IP of all
of the possible IPs is needed. Therefore one of the 13 being wrong is
inconsequential.
Because I've seen the named.root file as part of DNS server updates.
Thus updates to the DNS server also covers the named.root file.
> The addresses of the root servers did change on occasion in the past,
> and I would change my pdnsd config file in response.
Yes, they do occasionally change. I think I've seen three, or maybe
even four, changes in the 20 years that I've been working with them. I
think one or more of those changes was adding IPv6 addresses and not
actually a change of an IPv4 address.
> But I have not seen any change in a root server address in years and
> I am just wondering why they would indicate just a change in date.
Because the file that you are checking is created as a side effect of
something else changing multiple times a month. (At least that's my
understanding.)