Re: using runit as init

[Bernhard Graf <list-supervision@augensalat.de>]

Mike Buland wrote:

> In general, if you want to retain init-style runlevels, then you
> don't want to replace SysV init.  I have switched to runit entirely,
> it manages every service, and it does indeed support "runlevels." 
> See
> http://smarden.org/runit/runsvchdir.8.html for details.  Each runit
> runlevel is really just another service directory, runsvchdir changes
> which service directory you are using.  the runit "init" program is
> provided mainly for compatibility.
>
> There is no reason for runlevels to be numbered, and the kernel
> offers no support for runlevels, nor do any bootloaders.  When you
> pass 2, 3, 4, S, etc. to the kernel, it is ignored as an unrecognized
> parameter, but made available to running processes a number of ways. 
> Runit makes the commandline as well as any variables that are set on
> the kernel commandline available to the script 1 (and maybe 2 and 3,
> but I use it in 1).  Therefore if you set a variable in the
> bootloader on the kernel commandline named "runlevel" then you can
> use that in script 1 to change your runlevel.
>
> However, I would say based on the way you are using runit as process
> 1, you would probably be better off sticking with sysvinit and adding
> runsvdir to your inittab (a script very similar to the example script
> 2 provided with runit is just what you want).

As I wrote in my previous email I want an easy way to switch from SysV 
init to runit (or may be another one that supports process 
supervision). Since I have to care for a couple of production systems 
this switch must meet some conditions:
- full support for the old init system
- keep manual adjusting to a minimum

ATM I'm starting daemontools svscan from inttab on those hosts in 
addition to the normal SysV init stuff. This works but is not really 
pretty - I'd like to have a more consistent administration interface.

The goal is to install runit with RPM, reboot and then link the 
daemontools things into runit's service directory.

> As for the runlevel code, I got this from this very list a long time
> ago, give it a shot in script 1:
>
> # Set runlevel to:
> # - single       if kernel has param: S
> # - RUNLEVELNAME if kernel has param: runlevel=RUNLEVELNAME
> # - default      if kernel has no params or unable to set requested
> runlevel grep -q '\(^\| \)S\( \|$\)' /proc/cmdline &&
> runlevel='single' runsvchdir ${runlevel:-default} || runsvchdir
> default

Good tip! /proc/cmdline seems a smart way. Question 1 resolved. :-)

> utmp/wtmp support is done, I believe, through an external program,
> check out the getty*/finish scripts that are provided with the
> default distribution.

utmpset only clears lines from utmp, there is no way of setting anything 
as the name suggest.

-- 
Bernhard Graf