[LAU] JACK and realtime in Ubuntu 7.10

Pieter Palmers pieterp at joow.be
Sun Dec 2 05:14:20 EST 2007

Peter Clarke wrote:
> I'm having problems with realtime in JACK in my newly installed Ubuntu 7.10.
> If I start qjackctl as a normal user - even the user with "admin" privileges - 
> I cannot start the jack server in realtime mode.  The error is:
> cannot use real-time scheduling (FIFO at priority 10) [for thread -1210406208, 
> from thread -1210406208] (1: Operation not permitted)
> But if I start qjackctl with sudo, realtime works fine.
> I remember from my previous Gentoo system that I had to install modules 
> realtime and realtime-lsm, and the user had to be a member of group realtime.  
> But none of that seems to apply to Ubuntu, because it uses a specially 
> patched kernel; am I correct about that?
> Output of uname -a is:
> Linux peter-desktop 2.6.22-14-rt #1 SMP PREEMPT RT Mon Oct 15 01:05:51 GMT 
> 2007 i686 GNU/Linux
> The jackd command generated by qjackctl is:
> /usr/bin/jackd -R -dalsa -r44100 -p1024 -n4 -D -Chw:0,0 -Phw:0,0 -s -S -i2 -o2
> So my question is:  how can I run jack as a normal user in Ubuntu?

The easy way is to install the ubuntustudio packages that are part of 
the normal ubuntu repository. apt-get install ubuntustudio-audio should 
do the trick.

The thing to ensure is that your /etc/security/limits.conf contains 
these lines:

@audio   -  rtprio     99
@audio   -  memlock    512000
@audio   -  nice      -19

and that your user is part of the 'audio' group (it normally is by 

Normally the ubuntustudio packages take care of both these conditions. 
Note that should you have to add the lines or make your user member of 
the audio group, you have to logout and relogin in order for the changes 
to take effect.



PS: While you're at it you can also install the realtime patched kernel 
for ubuntu (linux-rt).

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