<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"
xmlns:ns0="http://www.exclaimer.co.uk">
<head>
<meta http-equiv=Content-Type content="text/html; charset=utf-8">
<meta name=Generator content="Microsoft Word 12 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]-->
<style>
<!--
/* Font Definitions */
@font-face
{font-family:Courier;
panose-1:2 7 4 9 2 2 5 2 4 4;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p
{mso-style-priority:99;
mso-margin-top-alt:auto;
margin-right:0in;
mso-margin-bottom-alt:auto;
margin-left:0in;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
p.2d8b867a-877d-4abf-9f71-702c0dd4ea36, li.2d8b867a-877d-4abf-9f71-702c0dd4ea36, div.2d8b867a-877d-4abf-9f71-702c0dd4ea36
{mso-style-name:2d8b867a-877d-4abf-9f71-702c0dd4ea36;
margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
span.EmailStyle18
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.EmailStyle19
{mso-style-type:personal;
font-family:"Arial","sans-serif";
color:navy;}
span.EmailStyle21
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=WordSection1>
<p class=MsoNormal><span style='color:#1F497D'>Yeah Jeff,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'>I was started to think that
also. I asked a few crusty Unix admins and they gave me a 500 yard stare.<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>
<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>Lightner, Jeff<br>
<b>Sent:</b> Tuesday, November 01, 2011 12:35 PM<br>
<b>To:</b> Atlanta Linux Enthusiasts<br>
<b>Subject:</b> Re: [ale] nsswitch and db option<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>I don’t think the stub resolver on Linux does any caching of its
own. That seems to be born out by this page which mentions that
some newer Windows stub resolvers do:<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><a href="http://www.zytrax.com/books/dns/apa/resolver.html">http://www.zytrax.com/books/dns/apa/resolver.html</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>So it seems if you wanted cache at client level on Linux you’d need
to implement something like BIND (or maybe TinyDNS which I haven’t worked with)
and have it get answers from upstream server. More work than I’d
want to do for most clients. I’d think if you had a single (or
better yet a pair) caching DNS server in your environment and had it in your
clients’ /etc/resolv.conf that the lookups should be quick enough for most
purposes without needing to cache at client level.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'>I’ve never used the db option in nsswitch.conf but based on what
little I can glean I don’t think it is for hosts but rather for things like
passwd, groups and shadow.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:navy'><o:p> </o:p></span></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36> <o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36> <o:p></o:p></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<hr size=2 width="100%" align=center>
</span></div>
<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>Chesser.Damon<br>
<b>Sent:</b> Tuesday, November 01, 2011 12:03 PM<br>
<b>To:</b> ale@ale.org<br>
<b>Subject:</b> [ale] nsswitch and db option</span><span style='font-size:12.0pt;
font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<div>
<div>
<div>
<div>
<div>
<p class=MsoNormal>I am trying to research the db option in nsswitch (as in:
hosts: db files dns ). We figure if a Linux client can use
the dns cache for lookups, that would be faster then files or dns.
However, I can’t find anybody who has ever used that option and google is slim
pickens researching it.<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>How do you access the (Linux) client dns cache info? Would
“hosts: db files dns” cause the first check to be performed on the dns
cache?<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>If NOT what does “db” cause to happen?<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Thanks!<o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal>Damon.chesser@suntrust.com<o:p></o:p></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> </span><span
style='font-size:12.0pt;font-family:Courier'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:Courier'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:Courier'> <o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>LEGAL
DISCLAIMER<br>
The information transmitted is intended solely for the individual or entity to
which it is addressed and may contain confidential and/or privileged material.
Any review, retransmission, dissemination or other use of or taking action in
reliance upon this information by persons or entities other than the intended
recipient is prohibited. If you have received this email in error please
contact the sender and delete the material from any computer.<br>
<br>
SunTrust is a federally registered service mark of SunTrust Banks, Inc. Live Solid.
Bank Solid. is a service mark of SunTrust Banks, Inc.<br>
[ST:XCL]</span><span style='font-size:12.0pt;font-family:Courier'> <o:p></o:p></span></p>
</div>
</div>
</div>
</div>
</div>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36> <o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36> <o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36><span style='font-size:10.0pt;
font-family:"Arial","sans-serif";color:fuchsia'>Athena</span><span
style='font-size:7.5pt;font-family:"Arial","sans-serif";color:fuchsia'>®</span><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:fuchsia'>,
Created for the Cause</span><span style='font-size:7.5pt;font-family:"Arial","sans-serif";
color:fuchsia'>™ </span><o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>Making a Difference in the Fight Against
Breast Cancer</span><o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36> <o:p></o:p></p>
<p class=2d8b867a-877d-4abf-9f71-702c0dd4ea36><span style='font-size:10.0pt;
font-family:"Arial","sans-serif"'>---------------------------------<br>
CONFIDENTIALITY NOTICE: This e-mail may contain privileged or confidential
information and is for the sole use of the intended recipient(s). If you are
not the intended recipient, any disclosure, copying, distribution, or use of
the contents of this information is prohibited and may be unlawful. If you have
received this electronic transmission in error, please reply immediately to the
sender that you have received the message in error, and delete it. Thank you.<br>
----------------------------------</span><span style='font-size:9.0pt;
font-family:"Courier New"'><o:p></o:p></span></p>
<p> <o:p></o:p></p>
</div>
</body>
</html>