Summary of S6-66 in Antix init diversity spin

Summary of s6-66 exploration


There was a long topic

in which I took a first look at the 66 Service Manager for the S6 init system.

I was fortunate to obtain assistance from

  • @ProwlerGR – the author of the init diversity spins
  • @Obarun – the author of the 66 service manager and also creator of the Obarun distro which is Arch Linux with S6-66.

It is time for a summary.
This is a stage summary, not a tutorial.

We are fortunate to have been able to see this important development in its early stages, and we appreciate the assistance of @ProwlerGR and @Obarun.

Please make any corrections or modifications. I have learnt something, but I am by no means an expert.

Brief history of init systems

Some of the things a running Linux system does are outside of the kernel. These are either

  • packages run in ‘user space’ , or
  • services ( also called daemon processes)
    Traditionally , after the kernel starts, it starts one process( called init) ,
    which consults some config files, which tell it what other daemon processses
    to start.
    Traditional daemon processes are slightly different to user-launched processes in that they are orphaned ( ie not owned by a shell). That mens they dont die, if you exit the shell… traditional daemons run forever… at least in theory.
    In practice, they die unexpectedly, and have to be manually restarted.
    That is the reality in a traditional init system like RC, sysVinit, or OpenRC.

At some point, it was decided that daemons need to be managed. That means that instead of fixing bugs in the daemon, we automatically restart it when it fails.
A whole spectrum of new init systems emerged – Upstart, Systemd, Runit, S6, Dinit, Shepherd.

Systemd has dominated in Linux, but not in BSD. It is the default in Debian, OpenSUSE, RHEL, and Arch.
Systemd has been criticized for violating Unix philosophy. It is large and a big learning curve. Systemd is like traditional init systems in that there is only one process running for each daemon started. A single process manages all running daemons.
Systemd is unlike traditional init systems in that it has parallel startup, users as well as root can manage services, and it has ways of managing multiple services as a group. (Correct me here if needed… I do not know systemd well).

The Runit and S6 init systems are different. They are both based on a package called ‘daemontools’, which manages daemons by having a separate supervise process ( in addition to the daemon process itself) running for each daemon. There may also be a logging process for each daemon, and a supervise process for the logging process… In this system , daemons are not orphaned, they belong to the supervise process.

Runit has supervision and parallel startup, , but not tools for service management( ie starting and stopping services) – you do it by hand, and no management of dependencies…

S6 has supervision plus service management, and it manages dependencies… The original service manager ( called S6-rc) has been available for some time, but has a few non-friendly concepts (such as compiling the database and writing execline scripts ) which make it clumsy to use. S6-rc has bundles which allow serveics to be grouped and managed as a unit.

There is a new service manager for S6 ( called S6-66) which has an elegant design and is much more user friendly. S6-66 avoids compiling a database, and it has a ‘frontend’ file instead of an execline script. 66 has ‘trees’, which are like bundles, and it allows users to manage services, as well as root.

This topic is about s6-66, but the background is important. In S6-66 we are looking at a facility with a substantially different philosophy to either systemd or traditional init systems.

My impressions after using s6-66 for several weeks

In S6-66 we are looking at an init facility based on couple of seriously
innovative academic initiatives.

  • the daemontools package is a set of tools for daemon management
    developed by the brilliant mathematician D J Bernstein, who has a number of papers on maths and computer algorithms.

  • the S6 part of s6-66 is a really thorough implementation of daemontools
    from It is this initiative which adds parallel startup
    and ****** dependency management ****** my error… it is 66 which adds dependency management… S6 supplies the daemontools implementation ( like Runit only more sophisticated)

  • the 66 part of s6-66 ( ie the service manager) is a design revolution
    for the user interface to init systems. There is only one command ( called 66) and there are subcommands. So it is designed like git or apt … the modern way to build a CLI command. There are no scripts … there is a user modifiable config file called a 'frontend` that sets up everything for a service… all in one place.

So we are dealing with something that is the combined product of a number of seriously innovative people. What you tend to get in such cases is something with a theory ( a philosophy if you like) behind it. In contrast software from large cooporate efforts tends to be a collection of poorly integrated tools with
inconsistent approaches

Concepts used by 66

It is important to understand the underlying ideas.

  • 66 – the name of the command that performs all Service Management actions ( except setting up a frontend file for a service). 66 has subcommands ( like git) and there is a help menu displayed by 66 -h or 66 <subcommand> -h

  • service – a process that runs automatically in background. The process is often called a daemon. Daemons in S6 ( and runit) are not orphaned the way they are in other init systems … they are owned by a supervise process which persists.

  • frontend – a user-written file providing information ( for setting up a service) from which 66 constructs and stores an execline script and other details. For root frontends are in ‘/etc/66/service’ and for normal users frontends can be in '~/.66/serviceor '/etc/66/service/user'. Frontends need to be accessed once with the66 parsecommand, and if they are altered need to be re-accessed with the66 reconfigure` command.

  • service type – classic, oneshot or module. Describes the way a service is used

    • classic service – a typical persistent daemon ( called longrun in s6-rc)
    • oneshot service – a service that performs one action then dies. ( for example a mount)
    • module service – a service ( or a bundle of services) whose actions can be modified at runtime by setting the environment. The names of services of type module end in ‘@’
  • instantiated – refers to the mechanism by which service actions can me modified at runtime. Any type of service can be instantiated. A module service is always instantiated. Instantiated services have an ‘@’ in their name ( eg tty@) and use an ‘@I’ in the frontend as a placemarker for a value substituted at runtime.

  • tree – a collection of services ( like a bundle in s6-rc) which
    can be managed together by one 66 tree ... command.
    There is a global tree which is the default and is present at install time.
    The ‘global’ tree is always enabled - ie it starts automatically at boot time.
    New services default to the global tree unless another tree is specified.
    There is a ‘boot’ tree which contains various services needed when the system boots.
    There is a tree called ‘session’ which containes modules which setup an environment in which a user can manage services.
    Other user-defined trees can be created. A service can only belong to one tree.
    Any type of service can belong to a tree, even a module service.
    A tree can not be nested within another tree.

  • enable/disable – something that is ‘enabled’ starts automatically at boot
    time. A single service can be enabled. A tree can be enabled.

  • stop/start – start means launch a service immediately. A tree can be started immediately. When a tree started, only the services within it that are enabled
    will start.

  • scandir – a directory ( /run/66/scandir/…) containing, for each user, the compiled version of the frontend for each running service, plus a number of status files. For root it is /run/66/scandir/0/…, for the first user it is /run/66/scandir/1000/… There is a special admin command to manage scandirs.
    The root scandir is automatically created. A user scandir must be initialised with the 66 scandir ... command, before any user services can be started.

  • boot@system – a special module that creates a tree called ‘boot’ that containes all the services needed for the system to boot properly.

  • boot-user@username – a special module that creates a tree called ‘session’ that contains modules which setup an environment in which a user can manage user owned services.

Setting up a frontend file

Each service requires a ‘frontend’ file. This is how services are configured.
Root frontend files are in /etc/66/service. User frontend files are in ~/.66/service.
When the system is installed, there will be some root frontend files present in /etc/66/service. These are useful as examples.

New services will require a ‘frontend file’ . We give a simple example of installing and starting a new service ‘vsftpd’.

apt install vsftpd

this makes sure the vsftpd binary is present.
We need to make a file called vsftpd in /etc/66/service containing

@description="vsftpd daemon"


‘classic’ means it is a traditional daemon, ie not a ‘oneshot’ or a ‘module’
this service can be started by root only
the binary is at /usr/sbin/vsftpd

This is a new frontend. It has to be parsed once

66 parse vsftpd`

Then it can be started

66 start vsftpd

***** not quite right… 66 start ... will do a 66 parse ... if it has not been done ******
If there is a mistake in the frontend, and you need to edit it, you then need to do

66 reconfigure vsftpd

which will re-parse it and re-start it.

That is all there is to starting a simple daemon.
There are more complicated things, such as setting environment variables, and defining dependencies between services.

Some examples of tasks and how to do it with 66

Everyone needs a recipe book. This is not comprehensive … just gives a taste of how easy 66 is to use.

Operating as root user

Start a service immediately

66 start <servicename>

Enable a service, so it will start at boot time.

66 enable <servicename>

Look at the status of a service

66 status <servicename>

Look at the available trees

66 tree status

To make a new tree you simply start a service specifying that tree

66 -t <newtree> start <servicename>

That will also add a service to an existing tree

To start a tree

 ****** 66 start <treename> ******** my error
66 tree start <treename>

ie, the same as starting a single service. All services within that tree will start if they have been enabled. You can use this to selectively start part of a tree by disabling unwanted services. If you want the tree to start automatically at boot
you have to enable the tree

 ***** 66 enable <treename> ****!**   My error
66 tree enable <treename>
Operating as non-root user

Before any normal user can use ‘66’ , root has to setup a module which establishes
the user environment. For example

66 parse boot-user@nevj
66 configure -e nano boot-user@nevj
edit the config ( eg set window manager)
66 reconfigure boot-user@nevj
always needed after a config is changed

there will then be a new tree called ‘session’

root@antix-init-diversity:~# 66 tree status

Name        : session
Current     : no
Enabled     : no
Allowed     : root
Groups      : admin
Depends     : None
Required by : None
Contents    : scandir@nevj:setenv@nevj scandir@nevj:svscan@nevj
              scandir@nevj:svscan@nevj-log scandir@nevj
              boot-user@nevj:mount-run@nevj boot-user@nevj

and it contains various module services which setup user ‘nevj’s’ environment

Now, each time ytyou boot you need root to do

66 start boot-user@nevj

and that sets up nevj’s environment.

Now user ‘nevj’ can use all the same 66 commands as in above examples for root.
User ‘nevj’ has his own global tree, which is separate from root’s global tree, and user ‘nevj’ can not see or manipulate the system trees.
Otherwise everything is the same as operating as root.

66 documentation

There is adequate documentation on the internet. 66 , as implemented in the init-diversity-spins, does not have man pages. However the source does have man pages, and they are present in Obarun Linux.

66 does have a help option

66 -h <subcommand>

will give a help page for the subcommand.

The '66’command:

Frontend files:



The toplevel page:



Beware of old versions… if you see anything like 66-start ... that is old
deprecated stuff.

Thank you again to all involved.


Thanks so much for this post :).
May i correct two or three little things?

It should be

66 tree start <treename>

same here, it should be

66 tree enable <treename>

Yes, it has to be parsed once but you get the same things shortly doing

66 start vsftpd

directly :). The call of this command involve the call of the parse subcommand…

S6 do not provide any dependency management. This is provided by 66 :slight_smile:

Really, thank you for your time on 66 to try it out and thank you for sharing your experience.


Oh Dear. Too many mistakes.
I will do a strikeout correction inline… dont want people being misled

Great summary @nevj & thank you for taking us along your journey of exploring 66
I did manage to pick-up a few things along the way & I’m sure all the interested readers would have learned a few things as well.
Eric @obarun has developed & constantly improving a great piece of software, which I hope to see make its way into many more linux & BSD distros.


If there is something that is misleading let me know… we need to flag it.
I have flagged the errors Eric noted.
Last thing we want is misinformation.

1 Like


Hi Neville, :wave:

what an incredible effort on your part. :+1:
That´s really a great summary/introduction to s6-66.

It´s very impressive that @obarun and @ProwlerGr could and were wiling to provide their invaluable help to you. :heart:

Yet - to be honest - I have to read through your article quite a few times more in order to fully comprehend it. I´m not nearly as knowledgeable as you, Neville.

Thanks again to all of you for this great treatise of yours.

Many greetings from Rosika :slightly_smiling_face:


Hi Rosika,
I think there is a need for a tutorial for S6 and 66.
It is very new, and at the moment there are only Obarun and the init diversity spins which have 66.
People are used to distros that have the init system fully set up and configured, but the only place you can find that with s6 init system is Artix, and that is s6-rc not s6-66.
Thank you for kind comments.

1 Like

yes, it does but this will depends of the distributor.

Thank you for that correction.
I will have a look in Oberun.

One question about Obarun.
I did an install from the latest JWM iso.
The live system has JWM, but when I install it in a VM it is a barebones Arch with just a console. Not even Xorg. I installed with sudo oberun install .
Is that deliberate?

1 Like

All this effort and expertise definitely deserves a proper page instead of just a forum entry.

What a great job (including the additional input)!


Thank you Mina,
How about you discuss with your itsFOSS team whether one of them would take on doing an S6-66 article? They could draw on the forum material, and I am sure @ProwlerGr and @obarun would assist with any questions.

I think the forum was the right place, while we were interacting. It is not over yet… I am working up to a topic on Obaron Linux with s6-66. That is the original source of 66…the init-diversity-spins drew on that and moved s6-66 into the Debian world.(Obarun is Arch)



The markdown files used to make this summary are
available here

All mistakes noted up till now have been corrected in the .md files.


I am not a member of the itsFOSS team. I just delete spam posts from time to time and (rarely) ban abusive users from the community. Why they allowed me to do so, I can’t say.

However: I know, @abhishek and @Ankush_Das regularly read the forum, and they might pick up the idea of making this topic a real article on the site.


This is practically an article, almost ready for publication. Good job!


Three things

  • lets be sure everything in it is dead right
  • could do with some pictures for FOSS style of article
  • it needs Abhishek’s ability to explain things at the right level for the average user.

Please ignore that.
I missed Option 3 Choose a desktop environment.
It defaults to minimal


That is way better than the video.

I have experienced the situation you warn about… dont try to restart the install if it fails… start again from the iso.
Some modern installers will let you go back , but the Obarun installer will not.