[Ubuntu Studio] Release Meeting 2012-01-27

[Scott Lavender]

On Fri, Jan 27, 2012 at 12:40 AM, Martin Pitt <martin.pitt at ubuntu.com> wrote:
> Scott Lavender [2012-01-26 22:45 -0600]:
>> * looks like live user isn't part of audio group which prevents rt privileges
>
> Can you please expand on this a little? We usually assign device
> permissions dynamically through ConsoleKit/PolicyKit these days.
>
> We can easily put the "ubuntu" user into the audio group in casper,
> but I wouldn't like to do this for users created in the actual
> install. This problem sounds like something that doesn't only affect
> the live system?
>
> Thanks,
>
> Martin
> --
> Martin Pitt                        | http://www.piware.de
> Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
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thank you for asking, martin.

the use of the 'audio' group is a method to grant improved real time
priority to help reduce latency for audio work (the -lowlatency kernel
is another pursuit of the same goal).

when jackd is installed, it creates /etc/security/limits.d/audio.conf,
in which is:

     @audio   -  rtprio     95
     @audio   -  memlock    unlimited

during installation, the created user will then be added to the 'audio' group.

setting memlock to 'unlimited' has admitted potential for denying
memory for a second user logged into the system.  however, ubuntu
studio is considered to be mainly a single user case, and given the
large size of some synth sample libraries available, it was weighed
and decided to follow this path.

thank you again,
scottl

p.s. i should also note that the lightdm bug is fairly critical as it
is reported to prevent x from starting.  the proposed solution
currently is to create a symlink (ln -s
/usr/share/xgreeters/lightdm-gtk-greeter.desktop
/usr/share/xgreeters/default.desktop)