Re: Address 127.0.1.1

From	Greg Wooledge <greg@wooledge.org>
Newsgroups	linux.debian.user
Subject	Re: Address 127.0.1.1
Date	2024-05-24 19:40 +0200
Message-ID	<IHH3A-fxQB-13@gated-at.bofh.it> (permalink)
References	(1 earlier) <IHEp3-fwe2-9@gated-at.bofh.it> <IHES5-fwCW-3@gated-at.bofh.it> <IHF1L-fwGk-3@gated-at.bofh.it> <IHFl7-fwN0-3@gated-at.bofh.it> <IHGhb-fxli-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, May 24, 2024 at 05:22:13PM +0100, Joe wrote:
> Long ago, lo used to be just 127.0.0.1, which is what most people would
> try to ping to check localhost, and what appeared in /etc/hosts. There
> is some subtle reason, which I used to know but have now long forgotten,
> why Debian started using 127.0.1.1 in /etc/hosts instead.

It's not "instead".  It's "in addition".

hobbit:~$ head -n2 /etc/hosts
127.0.0.1   localhost
127.0.1.1   hobbit.wooledge.org hobbit

The first line is traditional.  Exactly what it looks like.

The second line ensures that my hostname will always resolve to a
working IP address.  Lots of programs need that.  Some of the most
common reasons back in the old days were X clients that had been
told to use "myhostname:0" as their $DISPLAY.  If "myhostname" didn't
resolve to a working IP address (one which could contact the X server),
then X client programs wouldn't work.

A lot has changed since then, but the basic principle remains the same.
Some programs are going to expect to be able to open a network connection
to whatever IP address the system's hostname resolves to.  127.0.1.1
serves that purpose, without stepping on 127.0.0.1 which has its own
legacy role to fulfill.

Thread

Address 127.0.1.1 Paul M Foster <paulf@quillandmouse.com> - 2024-05-24 14:10 +0200
  Re: Address 127.0.1.1 Greg Wooledge <greg@wooledge.org> - 2024-05-24 14:20 +0200
  Re: Address 127.0.1.1 Dan Ritter <dsr@randomstring.org> - 2024-05-24 14:40 +0200
  Re: Address 127.0.1.1 Marco Moock <mm@dorfdsl.de> - 2024-05-24 16:50 +0200
    Re: Address 127.0.1.1 <tomas@tuxteam.de> - 2024-05-24 17:20 +0200
      Re: Address 127.0.1.1 <tomas@tuxteam.de> - 2024-05-24 17:30 +0200
      Re: Address 127.0.1.1 Marco Moock <mm@dorfdsl.de> - 2024-05-24 17:30 +0200
        Re: Address 127.0.1.1 Greg Wooledge <greg@wooledge.org> - 2024-05-24 17:50 +0200
          Re: Address 127.0.1.1 Paul M Foster <paulf@quillandmouse.com> - 2024-05-24 18:20 +0200
          Re: Address 127.0.1.1 Joe <joe@jretrading.com> - 2024-05-24 18:50 +0200
            Re: Address 127.0.1.1 Paul M Foster <paulf@quillandmouse.com> - 2024-05-24 19:20 +0200
              Re: Address 127.0.1.1 Andy Smith <andy@strugglers.net> - 2024-05-24 23:40 +0200
            Re: Address 127.0.1.1 Greg Wooledge <greg@wooledge.org> - 2024-05-24 19:40 +0200
      Re: Address 127.0.1.1 Joe <joe@jretrading.com> - 2024-05-24 18:50 +0200
        Re: Address 127.0.1.1 <tomas@tuxteam.de> - 2024-05-24 19:20 +0200
  Re: Address 127.0.1.1 Greg Wooledge <greg@wooledge.org> - 2024-05-24 19:50 +0200
    Re: Address 127.0.1.1 Jeffrey Walton <noloader@gmail.com> - 2024-05-24 20:00 +0200
      Re: Address 127.0.1.1 Greg Wooledge <greg@wooledge.org> - 2024-05-24 20:30 +0200
        Re: Address 127.0.1.1 debian-user@howorth.org.uk - 2024-05-24 23:30 +0200
  Re: Address 127.0.1.1 Jeffrey Walton <noloader@gmail.com> - 2024-05-24 19:50 +0200
    Re: Address 127.0.1.1 David Wright <deblis@lionunicorn.co.uk> - 2024-05-24 19:50 +0200

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