Designing a new init: low level communication

martin f krafft madduck at
Tue Aug 30 05:48:36 UTC 2005

also sprach Erich Schubert <erich.schubert at> [2005.08.29.0244 +0200]:
> 4. shared memory and sysv semaphores, or sysv messages
> Drawbacks:
> - difficult semantics, signalling?
> Pro:
> - portable to BSD? (can anyone verify?)


also sprach a-aa <a-aa at> [2005.08.29.1340 +0200]:
> You can use /dev, which means it's accessable from very early in
> the boot, initng does this and it works well.  Also, are we sure
> this needs a writable filesystem?  I think if the socket exists it
> might not, I can't really remember ;)

I think it would be a bug if you can write to a socket on an r/o

also sprach Erich Schubert <erich.schubert at> [2005.08.29.1401 +0200]:
> That only works with FIFOs IIRC - sockets will disappear when
> closed, so they only live for the runtime of the program. I don't
> know if they'll actually get a node on the disk.

No, they do not. They disappear when closed.

also sprach Erich Schubert <erich.schubert at> [2005.08.29.1704 +0200]:
> write "montior stdout,stderr" to the "toinit" fd, then read on "frominit"?

What does the daemon read from init in monitor mode?

init receives stdout,stderr anyway. Plugins can subscribe to those
streams, per daemon or as a whole. Then a plugin would handle simple
status output to the console, another could handle LSB output,
a third could handle a splashscreen.

I quite like the idea of using FDs for this.

also sprach Erich Schubert <erich.schubert at> [2005.08.29.1647 +0200]:
> What if it changes after the start of udev, with nothing else starting
> inbetween?
> It then would e.g. wait for a new start command, but can't recieve it
> due to the hidden socket?

I think it would work. If it aquired the filehandle, it will still
hold it even if udev now "obscures" the hierarchy. For the same
reason that all processes can still use files even after you
unlink() them.

also sprach Sven Mueller <debian at> [2005.08.29.2129 +0200]:
> To each his own. I would not forget about "runlevels" (I currently don't
> have a better name for it, perhaps "states" or "(service) collections"?)

profiles :)

 .''`.     martin f. krafft <madduck at>
: :'  :    proud Debian developer and author:
`. `'`
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