[Pkg-sysvinit-devel] Bug#638019: /run/initctl

[Roger Leigh]

On Sun, Jan 08, 2012 at 03:01:57PM +0100, Robert Millan wrote:
> El 8 de gener de 2012 15:00, Robert Millan <rmh at debian.org> ha escrit:
> > El 8 de gener de 2012 14:56, Roger Leigh <rleigh at codelibre.net> ha escrit:
> >> The postinst currently calls "init u", but I think that's problematic--
> >> it would call the new binary using the new path.
> >
> > On the contrary, isn't this precisely what we wanted? No symlink needed then.
> 
> Uhm, not sure if I understood correctly what "init u" does.  Anyway,
> I'd propose this approach:
> 
> - Create a new fifo in new path (no symlink).
> - Install new binaries (both sides) which use the new path.
> - Force init re-exec using a signal.
> 
> It seems much simpler than messing with symlinks or adding on-reboot
> triggered actions.

The problem is that there isn't a signal to force a re-exec.  You
have to do it through the control pipe.  "init u" sends the signal
through the pipe to trigger the re-exec, which requires that the
old pipe be present.  Because the new binaries will use the new
path, "init u" on its own won't work.  I would suggest this strategy:

1) Create /run/initctl
2) Symlink /dev/initctl (or /etc/.initctl) to /run/initctl
3) Send SIGUSR1 to init
   → init reopens using the old path, but is redirected to use
     /run/initctl
4) Wait for that action to complete
5) Run "init q" to re-exec init.  The new init will use the new
   paths
6) Delete the no-longer-needed /dev/initctl (or /etc/.initctl).


Regards,
Roger

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