Init : someone could comment this ?

[Enrico Scholz]

Nils Philippsen <nphilipp at redhat.com> writes:

> 1. process 1 (p1) prepares the service
> 2. when finished, p1 forks p2 which will be the long-runner, controlling
> any eventual children
> 3. p1 exits
>
> This seems to be a standard procedure for self-detaching daemons to
> me.

That's the old forking-daemon way. Most modern initsystems work best
with non-forking daemons.


> I've often had to chain multiple of these to get the desired results --
> but that's more a matter of convenience (perhaps my bash is just too
> rusty and it can be done more elegantly). What matters more to me (this
> came to mind only yesterday while driving home) is that if you do:
>
> cat $somefile | while read line; do ... done
>
> variables set in the while loop have no effect outside of it, or if you

this effect is known and this example can be written as

| while read line ... done < $somefile


But we are speaking about preparation scripts of daemons.  Do you really
need such tasks there?


> except OSError, e:
> 	# clean up OS error
> 	...
> except SomeException, e:
> 	# do something else
> 	sys.stderr.print "Warning: doing foo failed, continuing (%s)" % str (e)
> except:
> 	# panic!
> 	sys.stderr.print "Error: %s" % str(e)
> 	sys.exit (42)
>
> I don't know if any of this is necessary for init code, but these are
> some things that I miss or find cumbersome in shell.

I do not say that shell shall be used for everything. I just say that
python is not an option for any part of sysinit which should be written
completely in C.  (ba)sh plus usual POSIX/GNU tools are the optimal
choice for preparation tasks, but these are no deps of the sysinit
system itself but of the specific daemon.



Enrico