[TriLUG] How ssh et al resolves domain names...

Aaron Joyner aaron at joyner.ws
Tue Aug 27 10:18:23 EDT 2013


As an exercise, try the following commands, and see what you can glean
about what those commands are doing:

strace host mirawall -c1 2>&1 | grep open
strace ping mirawall -c1 2>&1 | grep open

Some of the things that show up in the latter, that don't show up in the
former, will be of interest to you.

Please do write back and summarize what you learn,
Aaron S. Joyner


On Tue, Aug 27, 2013 at 10:15 AM, Francois Dion <francois.dion at gmail.com>wrote:

> nsswitch.conf?
>
>
>
>
> On Tue, Aug 27, 2013 at 9:58 AM, Brian Henning <bhenning at pineinst.com
> >wrote:
>
> > Hi Gang,
> >
> > I think I've brought this topic up before, but it's back to taunt me
> again.
> > A snippet from my command line should summarize nicely:
> >
> > [brian at cheetah ~]$ host mirawall
> > mirawall has address 192.168.0.106
> > [brian at cheetah ~]$ ssh mirawall
> > ssh: mirawall: Name or service not known
> > [brian at cheetah ~]$ ping mirawall
> > ping: unknown host mirawall
> >
> > "mirawall" is a DHCP-assigned host on the local subnet.
> > dnsmasq provides DHCP and DNS.
> > "mirawall" is not in the /etc/hosts file, and I don't want it to be.
> >
> > Why does host(1) know who "mirawall" is, but ssh(1) and ping(8) (among
> > others) do not?  Shouldn't they all be resolving the hostname the same
> way?
> >
> > Is there some config file I need to tweak?  Here's my /etc/resolv.conf:
> >
> > [brian at cheetah ~]$ cat /etc/resolv.conf
> > ; generated by /sbin/dhclient-script
> > search nc.rr.com
> > nameserver 127.0.0.1
> > nameserver 8.8.8.8
> >
> >
> > Thanks,
> > ~Brian
> >
> > ------------------------------------------------------
> >           Brian Henning, Software Engineer
> >
> >     /\    Pine Research Instrumentation
> >    //\\   2741 Campus Walk Ave, Bldg 100
> >   ///\\\  Durham, NC 27705
> >  ////\\\\ USA
> >     ||
> >     ||    phone: 919.782.8320
> >           fax:   919.782.8323
> >           email: bhenning at pineinst.com
> > ------------------------------------------------------
> >
> >
> >
> > --
> > This message was sent to: Francois Dion <francois.dion at gmail.com>
> > To unsubscribe, send a blank message to trilug-leave at trilug.org from
> that
> > address.
> > TriLUG mailing list : http://www.trilug.org/mailman/listinfo/trilug
> > Unsubscribe or edit options on the web  :
> > http://www.trilug.org/mailman/options/trilug/francois.dion%40gmail.com
> > Welcome to TriLUG: http://trilug.org/welcome
> >
> --
> This message was sent to: Aaron S. Joyner <aaron at joyner.ws>
> To unsubscribe, send a blank message to trilug-leave at trilug.org from that
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>


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