[linux-audio-user] Re: ubuntu studio -rt

Dana Olson dana at ubuntustudio.com
Thu Feb 23 07:40:59 EST 2006


On 2/23/06, Ismael Valladolid Torres <ivalladt at punkass.com> wrote:
> Carlo Capocasa escribe:
> >
> > > group audio getting realtime only using PAM via
> >
> > I'm using the PAM binary package straight of ubuntustudio.com on Debian
> > Etch and it works like a charm.
> >
> > Carlo
> >
>
> I was missing that page! So there are three ways to get realtime,
> realtime-lsm which is deprecated (why, exactly?), set_rlimits which
> seems tricky, and the recommended rlimits aware PAM way. I am trying
> the last one, but libpam_modules at sid is 0.79 not 0.76, and I will
> need to recompile for powerpc and still don't know if patch will apply
> cleanly.

Carlo, there is more than one way to do EVERYTHING in Linux.

Realtime-lsm is convenient, and currently still available in Debian
and Ubuntu. It was a hack created due to kernel develops apparently
not listening to people who needed some method for non-root users to
run apps in realtime mode.

As of kernel 2.6.12, the kernel now has the capabilities to do what we
want. But the problem doesn't stop there, your system still needs some
way of knowing which users can run which apps with realtime
priorities. PAM is the way to do this. PAM 0.80 and newer do support
it OOTB, but as you know Debian and Ubuntu Dapper both currently have
0.79, so the patch is needed.

So why is set_rlimits even around? Well, not every distro even ships
with PAM. Slackware users don't have PAM. So they need a different
method to allow access to the rtprio capability. This app will work on
Debian and Ubuntu if you don't want to patch your PAM and don't want
to use the deprecated realtime-lsm.

I hope that sufficiently explains why there are three options. This
information has been discussed before as well, so I'm sure you could
have found it on your own, but here it is again, conveniently for you.

Now, to patch your 0.79 PAM, here are the steps for Dapper, should
work on Debian, just make whatever adjustments you need:

cd /tmp/
sudo apt-get install build-essential devscripts fakeroot
apt-get source libpam-modules
sudo apt-get build-dep libpam-modules
wget http://www.ubuntustudio.com/uploads/pam-0.79-rlimits.patch
cd pam-0.79/
mv ../pam-0.79-rlimits.patch debian/patches-applied/61-rlimits
patch -p1 < debian/patches-applied/61-rlimits
DEBEMAIL=pam at ubuntustudio.com dch -v 0.79-3ubuntu9studio1 Added patch
for rlimits, glibc hack, and default config.
debuild -us -uc
sudo dpkg -i /tmp/libpam-modules_0.79-3ubuntu9studio1_i386.deb

Dana.



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