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

[Reco <recoverym4n@gmail.com>]

On Fri, Sep 15, 2017 at 06:32:17PM -0300, x9p wrote:
> 
> > Your snippet of strace output on pastebin is lacking the beginning.
> > What I'm currently interested in are:
> >
> > 1) Libraries and configuration files that sudo is opening (hence the
> > 'open' syscall). Thinking about it, make it 'open,stat'.
> >
> > 2) What kind of network sockets (short of kinda obvious UDP) sudo is
> > opening (hence the 'connect' syscall).
> >
> 
> Sorry for that, pasted the full output here.
> https://pastebin.com/0bV7JC1z
> 
> > Feel free to edit out all unnecessary details of course.
> 
> No need.

Thanks, now I see it.

Your /etc/hosts says:

127.0.0.1       localhost
127.0.1.1       localhost
::1     localhost ip6-localhost ip6-loopback

Note the absence of localhost.localdomain.


Your hostname is "localhost.localdomain", as strace helpfully shows us:

uname({sysname="Linux", nodename="localhost.localdomain", ...})


I won't say that specifying fqdn as nodename is wrong per se, but in
your case you don't have a record for your hostname in /etc/hosts.

This *could* be the case that's nss-myhostname is designed for but …
it's the last in your nsswitch.conf so it cannot come into play.

Therefore libc resolver you're using does exactly the same way it's
supposed to - search for localhost.localdomain in /etc/hosts first,
query DNS next.


Quick and dirty way to fix this is to add a record for
'localhost.localdomain' in your /etc/hosts.

Correct, but painful way (I won't even try to predict what you could
break in your setup) to fix this is to ensure that your hostname is
'localhost' verbatim.

Reco