[ale] /etc/hosts and caching

[leam hall]

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.

Leam

On Fri, Nov 4, 2011 at 8:24 AM, Chesser.Damon <Damon.Chesser at suntrust.com>wrote:

>  Thanks for the reply, that is how I thought it worked also.  As for
> nscd, someone on this list said “Don’t.  Use. It.”  ****
>
> ** **
>
> Any other opinions on it?****
>
> ** **
>
> Damon at damtek.com****
>
> ** **
>
> *From:* ale-bounces at ale.org [mailto:ale-bounces at ale.org] *On Behalf Of *leam
> hall
> *Sent:* Friday, November 04, 2011 8:17 AM
> *To:* Atlanta Linux Enthusiasts
> *Subject:* Re: [ale] /etc/hosts and caching****
>
> ** **
>
> 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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