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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I would also like to see some facts, but google turns up tons of
“issues” with it (nscd). As a result we might be looking at installing Bind
DNS caching only on the servers we are talking about.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Damon@damtek.com<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> ale-bounces@ale.org
[mailto:ale-bounces@ale.org] <b>On Behalf Of </b>leam hall<br>
<b>Sent:</b> Friday, November 04, 2011 8:31 AM<br>
<b>To:</b> Atlanta Linux Enthusiasts<br>
<b>Subject:</b> Re: [ale] /etc/hosts and caching<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>I use it as it is turned on everywhere I've worked. I've not
seen any data that suggests it is a problem, but I'd be happy to see some
facts.<o:p></o:p></p>
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<p class=MsoNormal> <o:p></o:p></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'>Leam<o:p></o:p></p>
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<p class=MsoNormal>On Fri, Nov 4, 2011 at 8:24 AM, Chesser.Damon <<a
href="mailto:Damon.Chesser@suntrust.com">Damon.Chesser@suntrust.com</a>>
wrote:<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'>Thanks for the reply, that is how I
thought it worked also. As for nscd, someone on this list said
“Don’t. Use. It.” </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'>Any other opinions on it?</span><o:p></o:p></p>
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style='font-size:11.0pt;color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'><a href="mailto:Damon@damtek.com"
target="_blank">Damon@damtek.com</a></span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;color:#1F497D'> </span><o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
style='font-size:10.0pt'>From:</span></b><span style='font-size:10.0pt'> <a
href="mailto:ale-bounces@ale.org" target="_blank">ale-bounces@ale.org</a>
[mailto:<a href="mailto:ale-bounces@ale.org" target="_blank">ale-bounces@ale.org</a>]
<b>On Behalf Of </b>leam hall<br>
<b>Sent:</b> Friday, November 04, 2011 8:17 AM<br>
<b>To:</b> Atlanta Linux Enthusiasts<br>
<b>Subject:</b> Re: [ale] /etc/hosts and caching</span><o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Good
morning Damon!<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>As
far as I can tell by editing /etc/hosts on a RHEL 4 box, the IP addresses are
not cached longer than it takes me to edit the file. I believe your server will
alwyas look in /etc/hosts anyway, per the /etc/nsswitch.conf file. The normal
hosts line is something like: <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>
hosts: files dns<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>There
is the program nscd and it's config file, ncsd.conf. This configures some
caching for you but I *think* it's more DNS related than affecting /etc/hosts. <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Hope
that helps.<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'>Leam<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On
Fri, Nov 4, 2011 at 7:40 AM, Chesser.Damon <<a
href="mailto:Damon.Chesser@suntrust.com" target="_blank">Damon.Chesser@suntrust.com</a>>
wrote:<o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>This
dovetails into building a DNS caching server I asked earlier this week.
The issue is we are seeing latency in our application and a possible (but only
possible, not proven) issue might be host lookups. I figured that an
entry into /etc/hosts would be faster than a WAN DNS lookup especially since
the IP is static. Someone was concerned with disk reads and that becoming
a bottleneck. Someone else pointed out that /etc/hosts file was
cached. <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>This
started a google search by me to find out if that was true or not.
Totally inconclusive. Some have reported issues with not being able to
get the Linux box to re-read the hosts file after a change was committed short
of a reboot or init restart. Others have said just make the change and it
shows up. I have not found any documentation saying whether it was cached
or not. Any smart guys know the answer or can provide any documentation
on that? It’s kind of funny, you think you KNOW something until someone
says “Prove it”.<o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><a
href="mailto:Damon@damtek.com" target="_blank">Damon@damtek.com</a><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <span
style='font-family:Courier'> </span><o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-family:Courier'> </span><o:p></o:p></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-family:Courier'> </span><o:p></o:p></p>
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