[Beowulf] Users abusing screen

Prentice Bisbal prentice at ias.edu
Fri Oct 21 09:12:53 PDT 2011


On 10/21/2011 11:44 AM, Ellis H. Wilson III wrote:
> On 10/21/11 09:10, Prentice Bisbal wrote:
>> Beowulfers,
>>
>> I have a question that isn't directly related to clusters, but I suspect
>> it's an issue many of you are dealing with are dealt with: users using
>> the screen command to stay logged in on systems and running long jobs
>> that they forget about. Have any of you experienced this, and how did
>> you deal with it?
> 
> I think this is strongly tied to what kind of work the users are doing
> (i.e. how interactive it is, how long jobs take, how likely failure is
> to occur that they must react to).  In my personal experience the jobs I
> spawn aren't interactive, tend to take a long time, and because of point
> 2 require me to react pretty quickly to their failure or I lose out on
> valuable compute-time.  However, they are cumbersome to execute via a
> queuing manager (my work is in systems, so perhaps that area is an
> exception).  Therefore what I always do is just nohup myself a job, and
> tail -f it if I need to watch it.  I've adapted my ssh config such that
> I don't get booted off after 5 or 10 minutes without any input from me
> (I think the limit I set is like 2hours or something), so I can watch
> output fly by to my hearts content.
> 
> If I were you, I think the best way to avoid a user-uprising, but to
> achieve your goal is to give instructions on how a user can nohup (yes,
> just assume they don't know how) and how to configure ssh to not die
> after a short time.  This way they don't have to worry about getting
> disconnected if they aren't constantly interacting (so they can watch
> output), but they also aren't staying logged on indefinitely (since
> presumably their laptops/desktops aren't on indefinitely).
> 
> If you give them an alternative that is well defined with an example
> (not just, "Oh you can use such-and-such instead.") I can hardly believe
> they'll be all that upset.
> 

Ellis,

Using nohup was exactly the advice I gave to one of my users yesterday.
Not sure if he'll use it. 'man' is a very difficult program to learn,
from what I understand.

Prentice


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