Information for distribution packagers: non-slashpackage installations of s6 are now supported. You can now include s6 in your distribution, even if your filesystem policy forbids creating symbolic links in the root filesystem. You just have to remove the conf-compile/flag-slashpackage file and fill in the conf-compile/conf-install-* files before compiling, and voilĂ , FHS-ready s6. Same thing with all the other packages. Isn't life wonderful ?

What is it ?

s6 is a small suite of programs for UNIX, designed to allow process supervision (a.k.a service supervision), in the line of daemontools and runit.

The s6 documentation tries to be complete and self-contained; however, if you have never heard of process supervision before, you might be confused at first. See the related resources section below for pointers to more resources, and earlier approaches to process supervision that might help you understand the basics.



All these commands exit 111 if they encounter a temporary error or hardware error, and 100 if they encounter a permanent error - such as a misuse. Short-lived commands exit 0 on success.

Supervision system

s6-svscan and s6-supervise are the long-lived processes maintaining the supervision tree. Other programs are a user interface to control those processes and monitor service states.

Other daemontools-like utilities

These programs are a rewrite of the corresponding utilities from daemontools. The s6-log program is important in itself: it's a powerful, scriptable, general-purpose filtering and logging tool that can be used to entirely replace syslogd. It has many more features than its multilog counterpart.

Fifodir management, notification and subscription

These programs are a clean rewrite of the obsolete "pipe-tools" package; they are now based on a properly designed notification library. They provide a command-line interface to inter-process notification and synchronization.

Internal commands



Related resources

s6 discussion

Similar work

Other init systems

All-in-one init systems generally feel complex and convoluted, and when most people find out about the process supervision approach to init systems, they usually find it much simpler. There is a good reason for this.


s6 is one of the (late...) results of a long design discussion that happened in 2002-2003 on the supervision list and the log list. The main contributors to the thread were


Why "s6" ?'s small and secure supervision software suite.

Also, s6 is a nice command name prefix to have: it identifies the origin of the software, and it's short. Expect more use of s6- in future software releases. And please avoid using that prefix for your own projects.