[Discuss-gnuradio] Realtime scheduling with Linux kernel 2.6.24

[Patrick Strasser]

Hello!

To enable realtime scheduling the requesting process needs CAP_SYS_NICE. 
 Until now this meat running as root (and probably dropping all other 
capabilities), either as root user, via a wrapper or with sudo [1]. 
running as root initially is not preferable, but probably the most used 
practice.

With Linux kernel 2.6.24, file capabilities were enabled [2]. This means 
you can run your apps with predefined capabilities without unleashing 
the whole set powers at any time.

I manged to run ping without suid bit, and to run a minimal GNU Radio 
script that simply enables realtime scheduling, but only with adding the 
cabability to the python interpreter. I did not manage to assign the 
CAP_SYS_NICE capability to a script and run it so that enablig realtime 
scheduling was successful. It seems that I got the capability 
inheritance wrong or maybe it is not working at all and scripts can not 
be granted capabilities.

Did anyone have success until now with capabilities? I hope this will be 
working out, as it would get us rid of running scripts as root.

Patrick

[1] <address@hidden> 
http://thread.gmane.org/gmane.comp.gnu.radio.general/9789
[2] http://www.friedhoff.org/fscaps.html
--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at tugraz dot at>
Student of Telematik, Techn. University Graz, Austria