[auton-users] SSH sessions on LOPs

[Michael J. Baysek]

Hi Lab,

I've heard a few reports in the recent weeks about SSH sessions being
terminated for no apparent reason.  If this has happened, or happens to
you, here are some things to know:

     1. Our LOP/Q/R/S machines are not configured to time out your
        sessions.  Your sessions should last as long as you need them to.

     2. When sharing machines with other users, it is always possible for
        a job, or combination of jobs to overflow the memory in the
        machine.  When this happens, the kernel will go into self
        preservation, and will start killing unnecessary processes.  The
        kernel has this strange tendency [wink] to kill things that you
        may think are important, such as your jobs and bash sessions.
        This doesn't happen very often, but when it does, I usually catch
        it and notify you that it happened.

     3. If you sleep your laptop while connected to a LOP/Q/R/S machine,
        your SSH session should not be terminated.  The only reason the
        session would terminate is if your DHCP lease expired while your
        machine was sleeping, and upon wakeup, it received a different IP
        address from the DHCP server.

           1. For example, if sleep your laptop on wireless in Newell
              Simon, and walk elsewhere on campus and wake the machine,
              your connection should still be active.
           2. The connection may not be active if many hours have passed
              from the time you put your computer to sleep.
           3. If you sleep your laptop while plugged into a wired
              connection, and wake it without the wire, you will probably
              be disconnected, and vice-versa.
           4. If you sleep your laptop at home, and wake it at campus, you
              will be disconnected and vice versa.

     4. If you think you are timing out, please make sure that the TMOUT
        environment variable is either unset, or set to 0.  This will
        disable timeout in bash/tcsh.  The default setting in the lab is
        disabled.

     5. Check your client connection environment.
           1. In Linux you can find this in /etc/ssh/ssh_config.  Make
              sure that ConnectTimeout is 0 or disabled, and look for
              other timeout related options.  Make sure they are set to
              your liking.
           2. In Windows ssh clients like PuTTY, you will want to check
              all of the relevant tabs and save your preferences to the
              defaults in PuTTY.

     6. If you do get disconnected from a lab machine for apparently no
        reason, please notify me what machine and approximately what time
        the event occurred.



-- 
Michael J. Baysek, Systems Analyst
Carnegie Mellon University - Auton Lab
www.cmu.edu - www.autonlab.org
412-268-8939

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 3245 bytes
Desc: S/MIME Cryptographic Signature
URL: <https://mailman.srv.cs.cmu.edu/mailman/private/autonlab-users/attachments/20070227/4bc485e5/attachment.bin>