Re: How does host lookup work
On Mon, Mar 23, 2009 at 09:28:27PM +0000, Alan Chandler wrote:
> I am extremely confused about host lookup works now that avahi daemon
> has been added into the equation.
>
> my /etc/nsswitch.conf file has this in it for the host entry
>
> hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
>
> But as much as I google, I can find absolutely no explanation of what
> mdns4_minimal does.
>
> In particular - if one does a host lookup and its not found in files
> (presumably /etc/hosts) and not found by mdns4_minimal, does
> the "[NOTFOUND=return]" stop the lookup process from using the dns. (It
> clearly doesn't - so presumably mdns4_minimal does something else)
>
> Coupled with that - I am not sure if there is a command line command
> which uses this mechanism of host lookup. The man page for "host"
> command and the one for the "dig" command effectily say they are only
> doing a dns lookup.
>
> Why am I asking;
>
> I am doing some planning on how to change my home network when I (very
> shortly now) acquire a linux laptop.
>
> I will want to use it to develop some simple javascript/php/html/css web
> applications - and therefore will want to run apache web server.
> Ideally I would like a number of separate virtual hosts, for each
> separate application but
>
> a) When I am disconnected from the network I still need to see the host
> names (so I assume I use /etc/hosts to give aliases to localhost?)
Yes, though this will break any proper usage of those names, so you'll
eventually need to remove them.
> b) When I am connected to the local home network I want to have other
> people see these virtual hosts so that I can test some multiuser
> aspects of the applications. In this case, I could either use avahi to
> publish these names (although at the moment I can't quite work out
> how - it seems only to publish a single host name derived from
> the /etc/hostname), or make sure the names are properly identified in
> my local dns (I can allocate the IP address based on the mac address of
> the laptop thereby ensuring it always has the same one)
>
> But without understanding the basics, I can't really proceed to plan.
You can also check the host name resolution using
getent hosts some.hostname
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