On 14 Jan 2001, Nathan J. Williams wrote:

# Date: 14 Jan 2001 19:24:47 -0500
# From: Nathan J. Williams <nathanw@MIT.EDU>
# To: der Mouse <mouse@Rodents.Montreal.QC.CA>
# Cc: tech-kern@netbsd.org
# Subject: Re: Kernel <-> init communication for shutdown
# 
# > - They all send the same signal, but with a magic identifier somewhere
# >    in the stuff that gets passed to the signal handler.
# 
# You mean, the signal "code" parameter, where we already pass auxiliary
# signal information (albeit only for traps)?

After reading up on kill and company, I cannot see how an external process
can send anything else down that pipe!  That would really make it
difficult for that one to work.

# > - They don't kick init directly; instead, they cause the kernel to
# >    hand-craft a new process, which execs an executable appropriate to
# >    the key hit.  If the executable doesn't exist, the key is
# >    effectively ignored.  (This executable may, if it wants, kick init,
# >    in any of numerous ways.)
# 
# Too Much Magic. Even one hand-crafted process has always felt like too
# many.

Agreed.

I'd opt for a socket or some other hidden channel.

#         - Nathan

				--*greywolf;
--
*BSD: The Last Bastion of the true UNIX Religion.