For Linux 2.6, the Realtime Linux Security Module provides a relatively easy way for non-root users to gain real-time privileges. Some audio-oriented distributions include this module as a separate binary package or with the kernel image. Otherwise, you will need to download the realtime-lsm source and build it yourself.

This loadable kernel extension selectively grants real-time privileges to user programs. If loaded with modprobe realtime gid=29, it will permit real-time operation for all members of group 29 (the Debian "audio" group). It provides several additional options, described in the user documentation.

There is an allcaps=1 option, which duplicates the effect of running Linux 2.4 with the capabilities patch. To use that you must compile JACK with --enable-capabilites as you would for the 2.4 kernel. You will need this if you prefer to run jackstart -R rather than jackd -R. If you only use Linux 2.6, you need not bother with it.

Currently (as of 2.6.7) JACK has a serious problem creating SCHED_FIFO threads for real-time processing. It is unclear whether this is a bug in JACK, in the new Native PThreads Library (NPTL), or in the 2.6 kernel. At the moment no one has a solution, but there is a workaround: define LD_ASSUME_KERNEL=2.4.19 in the environment of the jackd process and of every JACK client. The easiest way to do this is setting it in ~/.profile , or wherever you customarily define global environment variables. Glibc developer Ulrich Drepper explains the operation of LD_ASSUME_KERNEL in more detail.