Re: Contents of /etc/hosts

[John Darrington <john@darrington.wattle.id.au>]

On Thu, Oct 06, 2016 at 12:07:37PM +0200, Hartmut Goebel wrote:
     Am 06.10.2016 um 02:57 schrieb John Darrington:
     >        127.0.0.1 localhost
     >        ::1       localhost
     >        127.0.0.1 gambrinus
     >        ::1       gambrinus
     >      
     >      Or am I missing something?
     >
     > Hmm.  I have never seen it done this way elsewhere, and I really wonder how some
     > services will react if they discover that 127.0.0.1 is not called "localhost"?  
     > Or that one address is known by two names.  I think it possible they might 
     > assume a security breach and refuse to work. 
     
     This should not be a problem. One could always add several entries for
     the same IP-address. And "getent hosts 127.0.0.1" will return the first
     entry in /etc/hosts AFAIKT.


     
     I started digging through the man pages, but did not finish. It's a deep
     maybe recursive mess of documentation where nothing is said about  Maybe
     we need to refer to the gethostbyname(2) and gethostbyname(3)
     documentation, which both are listed in "man hostname".

Indeed it is a mess.  And be careful there are several versions of "hostname" program
in circulation.  One of them explicitly says that

127.0.1.1 canoncal-name.example.com canonical-name 

Is the recommended way to set the canoncial name and fqdn
     
     * gethostbyname(2) [1], uses uname[2], which returns what ever has been
     set with sethostname (AFAICT) and always returns a single string.

That is also my understanding.
     
     * gethostbyname(3) [3] returns a structure capable to hold an name,
     several aliases, and several addresses.

Yes.
     
     Nevertheless my conclusion is that any program should be able to handle
     any ip-address and and hostname and must not rely on any assumtion
     regarding these. (Exept perhaps to assume "localhost" is defined.)

Well behaved programs should not make such assumptions.  But I don't think
we should assume that all programs behave well .
     

Anyway I think we need to change what we currently have because it breaks
"hostname -f" (and possibly other things too)

J'

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