:: Re: [DNG] how to clear DNS cache
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Lähettäjä: Simon Hobson
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Vastaanottaja: dng@lists.dyne.org
Aihe: Re: [DNG] how to clear DNS cache
jamey@??? wrote:

> I kind of like:
>
> A) Beginner
> B) Experienced
> C) Expert
> D) NetGod


Isn't this missing the point ?
If the problem is working around broken DHCP and/or local resolvers, then it comes down to :
A) If network configuration works and we can resolve the names we need to - then we don't need to ask the question at all. There's nothing to fix/workaround, no need for any user interaction.
B) Network configuration fails (IP address is gained, but DNS doesn't work) - then we have to start asking questions regardless of installation level. It comes down to starting down the route of "Your local network configuration appears to be broken, how do you want us to try and work around that ?".

IMO the initial options should be something a bit simpler, like (perhaps the ordering is wrong) :
[ ] Go back and retry network configuration
[ ] Manual DNS server entry ...
[ ] Try a public server ...
[ ] Try running a local resolver ...
[ ] Let the installer try a few things for you (automatic configuration based on tests) ...

Manual server entry is self explanatory - if you know of a working server, then bung it's IP address in.

Try a public server could then lead on to a dialog where the user is asked to pick one or more server(s) to try and use.

Similarly, Try a local resolver could ask the user which local resolver package to use - but IMO that's a bit moot as we should be able to run just one that's pre-defined for the duration of the install process and which "just disappears" when the ramdisk/tempfs/unionfs used by the installer goes away.

It probably makes sense to run some tests to determine if DNS lookups are actually possible. One logical approach would be to publish a dummy DNS entry (ie one not actually used for anything) just for the purpose of this - and with a known result. That way, the installer can be hard-coded with the response(s) it expects without the issues of it breaking when (for example) a repository server moves.

Try a few things might be a case of running a few tests to try and probe what the network allows. Perhaps see if the default gateway does DNS recursion for us, then try some known public (or root) servers and see if we get an answer. Depending on what we find, configure the installation environment automatically.


Rick Moen <rick@???> wrote:

> Without objection, I'll point out that one leading advantage of a local
> recursive server (what you probably mean when you say 'caching DNS
> server'[1]) is that it Just Works


Unless you are in one of the situations previously mentioned where it doesn't ...