[PlanetCCRMA] the jack permissions conundrum revisited

Jeff Sandys jpsandys at gmail.com
Fri Jul 23 12:34:40 PDT 2010

>> I am trying to understand this jack permissions conundrum.  You stated:
>> > - Fedora jack1 packages allows users access to realtime
>> > scheduling and memory locking only if the user belongs
>> > to a particular group (jackuser?).
>> I am not sure this is true.  When I load jack into fedora 13 from
>> fedora repositories, jackd is in group root and all users have
>> execution privileges.
> Easy to get confused. It is not the group of jack what matters, it is
> the group of the user that runs jack. Jack can be executed by anyone, as
> any other binary. But only users that belong to a certain group will be
> able to run it with real-time scheduling.

How can I figure out what group is able to run with real-time scheduling?
How can I tell if an application is using real-time scheduling?

>> If it is just a matter of creating a jackuser group and changing
>> jackd's group wouldn't it be easier to just create an instruction
>> sheet or small script for those who are concerned instead of creating
>> two versions of jack?
> This is done automatically for you when you install jack.
Would you need two separate versions of jack to achieve both the
fedora and PlantCCRMA real-time permission schemes or could the switch
be made with a script after installing jack (fedora-rt-mode.sh and

I have been using the CCRMA RT kernel almost exclusively since FC8
with no problems.  The only issues I had were with the nvidia akmod,
but now that nouveau supports openGL direct rendering I don't need to
worry about it.  I have had a few hangs, but I doubt that they were
due to real-time scheduling, more likely bad laptop hardware or app
found on the internet that I shouldn't have loaded.
Is there a way to tell if real-time scheduling was the culprit?

-- Jeff

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