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Old 06-23-2010, 12:46 PM   #1
Hal Itosis
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Question /etc/resolv.conf changed in Snow Leopard?

The contents of /etc/resolv.conf (or rather the target file /var/run/resolv.conf) seems to have some commentary now in Snow Leopard (which wasn't present in 10.5.x):

Code:
$ vis /var/run/resolv.conf
#
# Mac OS X Notice
#
# This file is not used by the host name and address resolution
# or the DNS query routing mechanisms used by most processes on
# this Mac OS X system.
#
# This file is automatically generated.
#
domain myipprovider.net
nameserver 123.45.67.89
nameserver 123.45.67.90
I find the word "not" there a bit puzzling. [i.e., what does this message mean?]

Is there a newer method (or an old one unbeknownst to me) to discover our DNS servers on 10.6.x client?

I also ask this because i've found a thread where the symlink /etc/resolv.conf has been replaced by an actual file. Isn't that possibly a cause for alarm... or is this the new norm?

Last edited by Hal Itosis; 06-23-2010 at 12:50 PM.
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Old 06-23-2010, 01:14 PM   #2
tlarkin
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I believe a lot of the DNS resolution in 10.6 actually goes through the mDNSresponder daemon now, which is used for network discovery and bonjour. I think this was due to a lot of issues where you would be inside your own internal network with your own DNS and then say VPN into another private network with their own Independent DNS and the system having issues resolving DNS because it was not doing proper reverse look ups to the right servers....

Where as in 10.5 lookupd and Directory Services did a lot of the DNS resolution. nslookup and changeip (changeip is for server only) were also used.

I also think that is why that file may be generated on the fly at times when you need access to a different DNS service say via VPN connection?

I am kind of guessing here based on what I have read on the SL changes from Leopard. It seems the concept is, if a server doesn't respond knock it to the bottom of the list for performance and efficiency. That is why that file is generated on the fly I think, that and issues of being part of multiple networks at once say via VPN.

http://support.apple.com/kb/HT4030

Above is a bit saying 10.6.3 modified DNS queries even a bit more, and they mention bonjour, which is what mDNSResponder daemon controls.

Other than that, I have not much clue outside of what I posted. Still learning 10.6 myself and finally have a 10.6 machine on my desk to play with
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Old 06-23-2010, 01:32 PM   #3
agentx
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It is all somewhat curious for me too, i would like to know what is going on ;-)
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Old 06-23-2010, 01:49 PM   #4
trevor
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There's a pretty good forum discussion of DNS in Snow Leopard at the link below:

Snow Leopard DNS & Directory Services

Trevor
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Old 06-23-2010, 01:53 PM   #5
tlarkin
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Quote:
Originally Posted by trevor
There's a pretty good forum discussion of DNS in Snow Leopard at the link below:

Snow Leopard DNS & Directory Services

Trevor

Nice, on a side note in that thread is a great link, here:

http://support.apple.com/kb/HT3789

Which goes over mDNSResponder daemon a bit
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Old 06-23-2010, 10:05 PM   #6
Hal Itosis
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Thanks for all the replies folks.
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