[erlang-questions] : : erl: "Can't set long node name!"

Raimo Niskanen <>
Thu Jun 19 14:44:19 CEST 2008


On Thu, Jun 19, 2008 at 07:04:12AM -0400, John Chandler wrote:
> On Jun 19, 2008, at 4:20 AM, Raimo Niskanen wrote:
> >On Wed, Jun 18, 2008 at 11:39:53PM -0400, John Chandler wrote:
> >>Thanks.  I think you may be right.  I'll have to work on how to set
> >>this up, because this is a Mac and the Unix networking tools only
> >>*sort of* work.  In particular, "hostname" doesn't have a "--long"
> >>option.
> >
> >On a Mac(OS X), `hostname' gives you the fully qualified
> >hostname and 'hostname -s' gives the short name. Try
> >`man hostname', it works on most platforms.
> 
> "hostname" works fine, it just doesn't have the same options
> as on Linux.  But if your network needs to be
> re-initialized, you can't use "ifconfig blah blah down" and
> "ifconfig blah blah up" to accomplish that, you have to do
> some GUI hoohah.  But I digress.  On my machine,
> "hostname" with or without the "-s" yields a
> fully-unqualified hostname.
> 
> >Why do you not run short names a'la `erl -sname foo'?
> 
> Because I am/was unaware of the option.  I am following an
> example in an online article that doesn't mention that those
> trying to follow along on a machine that boots up with DHCP
> from a consumer-level private-network router will get a
> not-entirely-helpful screenful of information and probably
> ought to use this other option.

That was nicely put. The error symptom has lots of
room for improvement, I agree.

Too bad the online article did not mention -sname...

> 
> >If you know your hosts DNS domainname you can force
> >the node name a'la `erl -name '.
> >
> >To make `erl -name foo' work, a name lookup of the
> >short hostname must return the fully qualified
> >hostname. Try from erlang with `inet:gethostbyname("foo").',
> >if that does not give you a long hostname as the
> >second element of the returned hostent tuple;
> >long node names will not work without giving
> >a long node name to the -name argument
> 
> This makes sense.  I have no particular commitment
> to using long node names, as long as I can get nodes
> to work properly without them.
> 
> >>
> >>Static IP may be a bit challenging, or at least laborious, because
> >>my machine is a laptop moved relatively frequently to different
> >>locations.
> >
> >It works just as well with dynamic IP, if the name
> >resolver (often DNS resolver) returns a fully qualified name.
> 
> There is no FQDN that resolves to my laptop, unless I'm
> mistaken.
> 
> >>
> >>And I'm not clear on how to set up a "domain" in the sense you
> >>mean.  I  have a couple of them, but they're not DNS'd to my
> >>laptop.
> >
> >If you have no clear domain, use short node names;
> >that is what they are for. Long node names are
> >only necessary when you have to distinguish between
> >different domains.
> 
> I think this may be the answer.
> 
> >>I wonder if Erlang will evolve to match the way people use
> >>computers now (and didn't 10, 20 years ago).
> >
> >I am afraid computer networking has not changed much
> >the last 10, 20 years...
> 
> My remark was ill-advised, and I apologize.  Erlang covers
> the case I'm concerned with, it's just the article I was
> following that didn't.  And I was reading the article in
> order to reduce, at least a little, my vast ignorance of
> Erlang.

Apology accepted. Either Erlang/OTP will have to evolve,
or maybe just OTP, or maybe just the applications
for Erlang/OTP.

> 
> Still, 10, 20 years ago people did not commonly pick up
> their computers, take them home, or to work, or to
> Charbucks, or to a friend's house, and (reasonably) expect
> them to be able to join the local net.  Back in the day, if
> you took your workstation to another branch of your large
> company, someone would have to add your MAC address to one
> NIS map, and give you an IP and a hostname before your
> machine would boot properly.

Quite right. And now such features as Zeroconf and Apple Bonjour
are emerging. We will see what features Erlang will need
to adapt. Erlang/OTP was designed for duplicated servers in
a static environment. Now computer networking is becoming
more dynamic, based on the old networking technology.

> 
> -jmc

-- 

/ Raimo Niskanen, Erlang/OTP, Ericsson AB



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