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Date: Tue, 25 Mar 1997 13:34:25 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199703250234.NAA06930@godzilla.zeta.org.au>
To: bde@zeta.org.au, rb@gid.co.uk
Subject: Re: 2.2R (src 2.2 211): <ctrl><alt><del> == dialing
Cc: freebsd-current@freebsd.org, joerg_wunsch@uriah.heep.sax.de,
        terry@lambert.org
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>>`man 2 _exit' says much the same things as POSIX about SIGHUP on exit.
>>It points to intro(2) for definitions of pg's/sessions.
>
>I was trying to complain that this description seems incomplete: the fact
>that live processes get signalled when multi-user operation ceases doesn't
>seem to be documented. In the case under discussion, the processes haven't
>exited.

This has nothing to do with POSIX signals or process groups.  It is much
simpler.  It is mostly documented in init(8):

1. If someone hits Ctrl-Alt-Del, then a SIGINT is usually sent to init.
2. Init shuts down and reboots when it receives a SIGINT.
3. Init shuts things down by broadcasting signals of increasing severity
   { SIGHUP, SIGTERM, SIGKILL }.
4. Some process like ppp do bad things when they receive a SIGHUP.

This differs from when the system is shut down using reboot(8).  reboot
shuts things down by broadcasting signals of increasing severity
{ SIGTERM, SIGKILL }.  I don't know why init broadcasts SIGHUP or why
reboot doesn't just signal init.

Bruce