Don’t Edit /etc/security/limits.conf

There are a number of sites that say to edit /etc/security/limits.conf.

The Cadence package from the KXStudio repository  automatically makes the entries for Jack in

/etc/security/limits.d/audio.conf and establishes the proper settings on installation.

The package automatically sets up Jack2 except for choosing the soundcard,  sample rate, buffer size, etc which you have to choose in the configuration menu of the application.

Qjacktl also sets these same parameters in its configuration menu.  They talk to each other, so you won’t screw things up by switching back and forth.  It is just that Cadence and Catia (Patchbay) are much easier to understand, and are prettier.

The debian.tryphon.eu  (This package no longer exists)   Rivendell package automatically sets them up in

/etc/security/limits.d/rivendell.conf

The priority and memory reservation for Jack are set in a file /etc/security/limits.d/audio.conf installed by kxstudio or qjackctl.  It is a good idea after installing to check that it has been installed.  It sets priority and memory reservations for the members of the  ‘audio’ group that should run jackd.  Files should be added here to set those applications with special needs for priority.

If you are using clamav malware and virus sniffer, its user should have a low priority “nice” level greater than 1 for its systemwide searches.  This is not automatically set, so you will need to make a  /etc/security/limits.d/clamwin.conf  file to limit clamwin’s consumption of resources.

The general philosophy with jack is to protect application’s priority by protecting the transport.  If you have a busy audio processor or something else that MUST run in realtime you might want to add a file for it in  /etc/security/limits.d/  reserving its necessary memory and a negative nice value closer to zero than that of Jack and Rivendell.   This is only needed if you have overruns or gaps or frequency or time shifts that are otherwise unexplained.

Another source of problems can come from hard drive partitions that are filled up.  Beware of backup programs, log files, etc. in a partition that is pretty full.  Ubuntu studio hangs up waiting for disk writes that never complete.