Can s6 be enough?: was s6-ps

[Steve Litt <slitt@troubleshooters.com>]

On Sat, 5 Jan 2019 10:46:29 +0000
Jonathan de Boyne Pollard <J.deBoynePollard-newsgroups@NTLWorld.COM>
wrote:


> s6 and s6-rc are actually ports/packages in FreeBSD and s6 is a
> package in Debian.  Alas, the Debian world has not yet caught up with
> the other toolsets, and the third-party Debian packaging for
> s6-linux-utils and the others has yet to make it into Debian's own
> repository.

This brings up a question I've had for a long time. Three years ago I
constructed an init consisting of Suckless Init as PID1 and s6 as the
supervisor, which was called at the end of a simple rc file forked by
Suckless Init. It worked just fine, without s6-rc or any other s6
products.

From discussions with Laurent I got the idea that the main added
functionalities of s6-rc are:

1) Process ordering during boot
2) Ability to intermix longruns with oneshots

Everybody appreciates the preceding two features, but personally, I
don't think they're absolutely necessary. Runit has neither, yet it
works just fine for most things. When I first switched to runit, with
its indeterminate ordering, I figured that with the dependencies I
built into the run scripts,  boot would resemble a field of mousetraps
throwing ping pong balls. But that wasn't the case: runit brought
everything up quickly and without trouble.

So I'm thinking that although process ordering and intermixing are
features we'd everyone likes, all but the most discerning among us
could get along without them and therefore init with s6 alone.

This is more than theoretical. As you remember, Debian's runit package
manager wrote to ask about a minor problem with too many .u files and
was contemplating changing some code, but nobody knew the code
intimately, and runit is pretty much unmaintained at this point. So I
suggested s6, which apparently has a Debian package but not one for
s6-rc. My opinion is one can boot just fine with s6 alone, as long as
you're willing to forego startup ordering and intermixing of longruns
and oneshots, which by definition a runit fan is.

So what do you all think? Is s6 a useful init system without s6-rc?

Thanks,
 
SteveT

Steve Litt 
January 2019 featured book: Troubleshooting: Just the Facts
http://www.troubleshooters.com/tjust