[Beowulf] Users abusing screen

Mark Hahn hahn at mcmaster.ca
Wed Oct 26 16:55:13 EDT 2011


> sometime, and I've never seen a comment like yours before. You're out of
> line.

hah.  Greg doesn't post all that much, but he's no stranger to the flame ;)

seriously, your question seemed to be about a general problem,
but your motive, ulterior or not, seemed to be to get rid of screen.

IMO, getting rid of screen is BOFHishness of the first order.
it's a tool that has valuable uses.  it's not the cause of your problem.

on our login nodes, we have some basic limits (/etc/security/limit.conf)
that prevent large or long processes or numerous processes.

* hard as 3000000
* hard cpu 60
* hard nproc 100
* hard maxlogins 20

these are very arguable, and actually pretty loose.  our login nodes are
intended for editing/compiling/submitting, maybe the occasional gnuplot/etc.
there doesn't seem to be much resistance to the 3G as (vsz) limit, and 
it does definitely cut down on OOM problems.  60 cpu-minutes covers any
possible compile/etc (though it has caused problems with people trying to
do very large scp operations.)  nproc could probably be much lower (20?)
and maxlogins ought to be more like 5.

we don't currently have an idle-process killer, though have thought of it.
we only recently put a default TMOUT in place to cause a bit of gc on 
forgotten login sessions.

we do have screen installed (I never use it myself.)

regards, mark hahn.
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