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Re: [K12OSN] ssh issue with LDM



Jim,

Thanks!  The contents of /etc/hosts and /etc/resolv.conf are (with
lines now commented out)

dhopkins ncslts1:~> cat resolv.conf
127.0.0.1    localhost
#127.0.1.1    ncslts7
# The following lines are desirable for IPv6 capable hosts
#::1     localhost ip6-localhost ip6-loopback
#fe00::0 ip6-localnet
#ff00::0 ip6-mcastprefix
#ff02::1 ip6-allnodes
#ff02::2 ip6-allrouters
#ff02::3 ip6-allhosts
dhopkins ncslts1:~> cat resolv.conf
#domain ncs.k12.de.us
search ncs.k12.de.us
nameserver 10.179.2.6
#nameserver 10.1.1.10
#nameserver 10.1.1.11

What is extremely strange is that there were not any issues at all and
then this issue started.  In the past, I have been able to track these
issues back to the configuration of the router (to which I have no
access, it is State controlled/configured).  I'll add a local hosts
file and see if this improves performance.

Sincerely,
Dave Hopkins

On Wed, Dec 14, 2011 at 10:08 PM, Jim Kinney <jim kinney gmail com> wrote:
> ssh does a reverse lookup to try and identify the far end of the connection.
> If the remote end doesn't resolve by a dns lookup, things get very, very
> slow. You can have an /etc/hosts file be sufficient as long as the
> /etc/nsswitch file is set to try hosts firsts (default).
>
> The TCs don't have a populated hosts file so they rely on DNS.
>
> Unless you supply a hosts file from the servers supply side /etc area for
> the TCs.
>
> On Wed, Dec 14, 2011 at 7:05 PM, David Hopkins <dahopkins429 gmail com>
> wrote:
>>
>> All,
>>
>> I am beginning to suspect this issue is because ssh isn't resolving
>> names correctly?  Timing
>>
>> ssh myserver
>>
>> from a shell (ALT-CTL-F2) takes about 30 seconds to resolve myserver.
>> However, ssh any_other_server returns immediately.  So, why wouldn't
>> myserver resolve quickly?  This is true from any of the servers ..
>> they do not resolve their names quickly.  On all of them, the local
>> (thin client) /etc/hosts has the form
>>
>> 127.0.0.1 localhost
>> 127.0.0.2 ltsp50
>> 192.168.0.254 server
>>
>> where the thin client is lstp50 ... but ... server is not defined in
>> DNS, only in the thin clients /etc/hosts.  Logging in at the console
>> for any account also works.
>>
>> This is very very very confusing and unfortunately, come tomorrow
>> morning is going to be a major issue.
>>
>> Sincerely,
>> Dave Hopkins
>>
>>
>>
>> On Wed, Dec 14, 2011 at 6:13 PM, David Hopkins <dahopkins429 gmail com>
>> wrote:
>> > We are having a major issue with thin client authentication. It
>> > started just after lunch time today. Authentication works fine from
>> > console and on terminal, but ssh takes a very long time to connect.
>> > One server (out of 5) can still connect though the login process takes
>> > quite a while to complete.  However, it is shorter than the other
>> > servers, so we suspect it is a timeout issue with LDM.
>> >
>> > From a shell at the thin client I can ssh to any system and
>> > authenticate.  However, trying to ssh from a shell at the client to
>> > the ltsp server that the client is connected to takes a very long
>> > time.  The response at the GUI login screen is "no response from
>> > server, restarting". We have already updated the sshkeys and
>> > completely rebuilt the image but this hasn't resolved the issue. How
>> > does LDM use ssh for authentication? Is there a reason ssh would have
>> > to be routed?  And .. why would ssh to any system except the system
>> > that the client booted from take so long?  We have enabled
>> > IP_Forwarding at the clients for localapps and that also works if that
>> > information is of any use.
>> >
>> > Any help is greatly appreciated!
>> >
>> > Sincerely,
>> > Dave Hopkins
>>
>> _______________________________________________
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>> For more info see <http://www.k12os.org>
>
>
>
>
> --
> --
> James P. Kinney III
>
> As long as the general population is passive, apathetic, diverted to
> consumerism or hatred of the vulnerable, then the powerful can do as they
> please, and those who survive will be left to contemplate the outcome.
> - 2011 Noam Chomsky
>
> http://heretothereideas.blogspot.com/
>
>
> _______________________________________________
> K12OSN mailing list
> K12OSN redhat com
> https://www.redhat.com/mailman/listinfo/k12osn
> For more info see <http://www.k12os.org>


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