Re: sudo slow on DNS lookup, with invalid resolv.conf entries

From	Brian <ad44@cityscape.co.uk>
Newsgroups	linux.debian.user
Subject	Re: sudo slow on DNS lookup, with invalid resolv.conf entries
Date	2017-09-19 00:00 +0200
Message-ID	<urcf7-3Gm-7@gated-at.bofh.it> (permalink)
References	(4 earlier) <uqYc9-2wo-1@gated-at.bofh.it> <ur7fs-fa-23@gated-at.bofh.it> <ur8Oe-1p3-23@gated-at.bofh.it> <ur9hg-1yZ-19@gated-at.bofh.it> <urb9o-2X2-11@gated-at.bofh.it>
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On Mon 18 Sep 2017 at 23:47:18 +0300, Reco wrote:

> On Mon, Sep 18, 2017 at 07:48:53PM +0100, Brian wrote:
> > On Mon 18 Sep 2017 at 20:13:44 +0200, deloptes wrote:
> > 
> > > Reco wrote:
> > > 
> > > > The question is - since 'localhost.localdomain' is special, what happens
> > > > if such hostname is chosen during the installation?
> > > 
> > > well, now we all know what happens :)
> > 
> > True, we know the OP has a problem with with sudo.
> 
> That's what lie on surface. Any software that implements
> uname/gethostbyname sequence would exhibit similar behavior.
> 
> 
> > What we do not know
> > is the hostname he chose during the installation, although it looks like
> > it was "localhost" from the second line of
> > 
> >   127.0.0.1       localhost                                                                                             
> >   127.0.1.1       localhost
> 
> I agree.
> 
> > The installer recommends a single word for the hostname. The "single"
> > aspect is the result of a number of years of experience and bug reports.
> 
> And let's not forget RFC 952 (obsoleted by RFC 1123), which states:
> 
> A "name" (Net, Host, Gateway, or Domain name) is a text string up to 24
> characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-),
> and period (.).  Note that periods are only allowed when they serve to
> delimit components of "domain style names".
> 
> RFC 1123 lifts some restrictions:
> 
> One aspect of host name syntax is hereby changed: the restriction on the
> first character is relaxed to allow either a letter or a digit.  Host
> software MUST support this more liberal syntax.
> 
> Host software MUST handle host names of up to 63 characters and SHOULD
> handle host names of up to 255 characters.
> 
> But does not says anything about dots, so restrictions of RFC 952 still
> apply.
> 
> > Although "localhost.localdomain" is not an invalid hostname
> 
> I agree as long as 'invalid' is defined as 'kernel does not accept it'.
> For instance, one can set nodename as 'localhost.local' and watch avahi
> explode. Or, say, '_localhost', if one intends to wreak havoc in local
> DNS's SRV records.
> The kernel is surprisingly liberal at these things.
> 
> > the OP does not appear to have used it. (We have not been given the
> > contents of his /etc/hostname explicitly).
> 
> True. We also did not see the contents of sysctl.conf (and those *other*
> files that can store kernel tunables), custom init.d scripts and custom
> systemd units if there were any.
> 
> To make things more confusing, 'localhost.localdomain' could be a
> 'transient' hostname, not a 'static' one (aka /etc/hostname).
> 
> It's one of those things I prefer to debug with auditd on. Too many
> possibilities otherwise.
> 
> > What was the problem with his resolv.conf? Have I missed that?
> 
> OP used an unspecified VPN client which put an additional entry into
> /etc/resolv.conf on start, but failed to clean it up on stop.

Much clearer now. Your attention to explaining in detail is appreciated.

-- 
Brian.

Thread

sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 18:10 +0200
  Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 19:00 +0200
    Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 21:30 +0200
      Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 22:00 +0200
        Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:10 +0200
          Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-15 23:20 +0200
            Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:40 +0200
              Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-16 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-16 01:20 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-16 02:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-17 22:40 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-17 23:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 00:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 01:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 01:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 09:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-18 18:40 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 20:20 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 20:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Reco <recoverym4n@gmail.com> - 2017-09-18 22:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-18 22:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries deloptes <deloptes@gmail.com> - 2017-09-18 23:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-19 00:00 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-19 00:10 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Gene Heskett <gheskett@shentel.net> - 2017-09-18 00:50 +0200
                Re: sudo slow on DNS lookup, with invalid resolv.conf entries Brian <ad44@cityscape.co.uk> - 2017-09-18 01:20 +0200
  Re: sudo slow on DNS lookup, with invalid resolv.conf entries Dan Ritter <dsr@randomstring.org> - 2017-09-15 23:10 +0200
    Re: sudo slow on DNS lookup, with invalid resolv.conf entries "x9p" <debian-user@x9pneu.com> - 2017-09-15 23:40 +0200

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