[ale] /etc/hosts and caching

[leam hall]

Good morning Damon!

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:

   hosts:      files dns
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.
Hope that helps.

Leam

On Fri, Nov 4, 2011 at 7:40 AM, Chesser.Damon <Damon.Chesser at suntrust.com>wrote:

>     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.  ****
>
> ** **
>
> 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”.****
>
> ** **
>
> Damon at damtek.com****
>
> ** **
>
>
>
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Mind on a Mission <http://leamhall.blogspot.com/>
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