Re: Sendmail takes ages to start at bootup

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On Fri, 2007-12-21 at 01:25 +1030, Tim wrote:
> On Thu, 2007-12-20 at 23:06 +1100, Simon Slater wrote:
> > Soooo..., going back to kindergarten..., the names I put in /etc/hosts
> > were made up to describe the box on a purely internal network.  Should
> > the names/aliases be something different?  What would/would not
> > conflict with public FQDN? 
> Given that intro, I can't resist some fun with domain names...
> 
> If you have SMTP server running on a machine called bluecrayons (the
> machine's hostname), then that machine needs to be able to resolve
> addresses in a way that makes sense to itself at start up.  It'll try to
> resolve the name as the server starts up.  It needs to be able to
> resolve those addresses, to itself, at least.
> 
> A sample hosts file entry:
> 192.168.0.1 bluecrayons.example.com bluecrayons mail smtp
> 
> That's an IP address, a FQDN, and a list of three aliases that you might
> have used (the hostname, a bog standard "mail" hostname, and another
> common "smtp" hostname).  The latter two aliase being things that some
> people pick out of habit, but there's nothing saying you must do so,
> though it does make simple sense to users to configure mail.example.com
> as their mailserver).
> 
> Your mail server can start up disconnected from a network, and that's
> all it'll care about (its own addressing - that out of the interfaces
> it's using, the addresses resolve).  It can start up connected to a
> network, and the same applies.  Thus far, that's all for internal
> purposes.
> 
> However, something from outside connecting to your mail server is going
> to expect a public name to match a public IP address.  You could have
> the same hostname/domain names, and external DNS servers use the
> external IP address to the machine, and internal DNS servers giving a
> different IP address to other local machines.
> 
> e.g. An outside DNS server might associate 208.77.188.166 with
> bluecrayons.example.com.  Outside services would connect to you using
> that FQDN or IP, and since they both resolve against each other,
> externally, those outside services are happy about it.
> 
> As for what won't conflict, don't make use of real domain names
> belonging to someone else, or make up ones that might be registered by
> someone at some time.
> 
> An IP address is how you connect between A and B.  A and B might have
> more than one address.  Which one is used depends on the networking.
> 
	The lights have just come on, physically and metaphorically!  A
thunderstorm has sat over the area for most of the day with power on and
off all day, so I left the mail til now.  Ever read all you can lay your
hands on and still seemed in the dark?  The light has turned on now.

	I realise now what I have done and how to fix it.  Too late to start
now.  First thing tomorrow.  Many thanks.

-- 
Regards
Simon

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