Incompatibilities between runit and s6?

Incompatibilities between runit and s6?

[Charlie Brady]

Has anyone tabulated technical differences between runit and s6? I'm 
considering migrating some systems which use runit to supervise some of 
their services (systemd the others - they're CentOS based). I am wondering 
whether I can write a wrapper caled "sv" which calls s6-svc with the 
appropriate argument rewriting, to avoid needing to find and modify many 
scripts. Has anyone written such an 'sv' command already?

I'm disappointed that the documentation is so dismissive of using s6 
process supervision on a system which uses systemd as init.

https://skarnet.org/software/s6/s6-svscan-not-1.html

 If you are a systemd user, chances are you do not need s6.

Really? So all the criticism of systemd is bunkum?

https://skarnet.org/software/s6/systemd.html

 If you are interested in using s6, I encourage you to also stop using systemd.

Not practical.

Re: Incompatibilities between runit and s6?

[Laurent Bercot]

>Has anyone tabulated technical differences between runit and s6? I'm
>considering migrating some systems which use runit to supervise some of
>their services (systemd the others - they're CentOS based). I am 
>wondering
>whether I can write a wrapper caled "sv" which calls s6-svc with the
>appropriate argument rewriting, to avoid needing to find and modify 
>many
>scripts. Has anyone written such an 'sv' command already?

  I'm not aware of such a command, but s6-svc supports everything sv
does, so writing such a script should not be hard. The only difficulty
is if the service uses a ./check file, which "sv start" supports
natively but s6-svc does not, so the wrapper would need to perform
the ./check polling itself; but the best thing to do in this case
is to rewrite the run script to use s6-notifyoncheck, so the check
automatically uses the s6 readiness notification framework.


>If you are a systemd user, chances are you do not need s6.
>
>Really? So all the criticism of systemd is bunkum?

  :) I need to update this page.
  What this means is that systemd does provide a supervision
infrastructure, so for people stuck with systemd, it's okay to use what
their system provides, and s6 is redundant there. This does not mean
that all my systemd criticism is invalid.

  Also, admittedly, I simply did not want to read the systemd unit file
documentation to understand how to start a s6 supervision tree from
systemd. I will do the effort and come up with a small unit file
suitable for this.

--
  Laurent

Re: Incompatibilities between runit and s6?

[Charlie Brady]

On Wed, 10 Jan 2018, Laurent Bercot wrote:

> >If you are a systemd user, chances are you do not need s6.
> >
> >Really? So all the criticism of systemd is bunkum?
> 
>  :) I need to update this page.
>  What this means is that systemd does provide a supervision
> infrastructure, so for people stuck with systemd, it's okay to use what
> their system provides, and s6 is redundant there. This does not mean
> that all my systemd criticism is invalid.
> 
>  Also, admittedly, I simply did not want to read the systemd unit file
> documentation to understand how to start a s6 supervision tree from
> systemd. I will do the effort and come up with a small unit file
> suitable for this.

Thanks. I would rather you write one small unit file then me needing to 
write ten or fifteen of them.

I agree with you about the systemd unit file documentation. That's exactly 
why I still need runit or s6. Well, one of the reasons.

Re: Incompatibilities between runit and s6?

[Jonathan de Boyne Pollard]

Laurent Bercot:

> Also, admittedly, I simply did not want to read the systemd unit file 
> documentation to understand how to start a s6 supervision tree from 
> systemd. I will do the effort and come up with a small unit file 
> suitable for this.
>

* https://lists.debian.org/debian-user/2014/09/msg01715.html

* http://jdebp.info./FGA/inittab-is-history.html

* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=752075#82

Re: Incompatibilities between runit and s6?

[Laurent Bercot]

>Thanks. I would rather you write one small unit file then me needing to
>write ten or fifteen of them.

  Done.
  https://skarnet.org/software/s6/s6-svscan-not-1.html#systemd

  I did not follow Jonathan's suggestion to use a .path unit file,
because the other examples on this page assume that the scandir
is already present at boot time, and there's no need to burden
the poor system with one more inotify watch. :)

--
  Laurent

re: Incompatibilities between runit and s6?

[Charlie Brady]

On Wed, 10 Jan 2018, Avery Payne wrote:

> I am guessing the differences will be subtle, and most of the general
> behavior you desire will remain the same.  You may be able to get a way
> with a "sed 's/sv\ /s6-sv\ /' <old-script-name >new-script-name" on some of
> your scripts; give it a try, what could it hurt?

That would fail because, eg, 'sv t xxx' needs to become 's6-svc -t xxx'.  

> Also, for those systems not running CentOS, what are you currently using
> for init + service management?

That's actually a null set, except for some old embedded systems running 
busybox init+runit.

re: Incompatibilities between runit and s6?

[Avery Payne]

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I am guessing the differences will be subtle, and most of the general
behavior you desire will remain the same.  You may be able to get a way
with a "sed 's/sv\ /s6-sv\ /' <old-script-name >new-script-name" on some of
your scripts; give it a try, what could it hurt?

Also, for those systems not running CentOS, what are you currently using
for init + service management?