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From: braun@drivax.UUCP (Kral)
Newsgroups: comp.unix.questions
Subject: unmounting file systems
Message-ID: <1734@drivax.UUCP>
Date: Tue, 2-Jun-87 13:35:28 EDT
Article-I.D.: drivax.1734
Posted: Tue Jun  2 13:35:28 1987
Date-Received: Sat, 6-Jun-87 12:03:31 EDT
Reply-To: braun@drivax.UUCP (Kral)
Organization: Digital Research, Inc.
Lines: 46


The discussion a few months ago regarding autodump procedures inspired me to
push on with my own autodump procedures I had started a few months earlier.
I have the major task down, but some of the details are really beginning to dig
in.  I am running 4.2BSD on an 11/780 with a TU78, RM03, and an RP07.

The basic algorithm runs like this.  At the designated time I run a script
which takes the system down to single user mode.  This is achieved by:

	running a script which returns 0 status if no one else is logged in,
	else returns a non-zero status.  If no one is logged in, the system is
	shutdown immediately.  Otherwise the system is shutdown in 5 minutes.

	/.profile is set to search for a particular file.  If it exists, it
	takes the first line of the file as a command to execute.  Before
	executing the command, it unmounts the file system (umount -a).  If the
	command finishes successfully, it reboots to multi-user mode.
	Otherwise it sits in single user mode for an operator to take
	appropriate action.

I have several problems, but the one I wish to address here is a problem with
automatically unmounting all partitions reliably.  The main culprit seems to be
the line printer spooler.  If there is anything spooled (say a printer is out
of paper and one or more jobs are waiting) then /usr won't unmount.  This isn't
really a problem as far as the backups are concerned, but when the system
reboots and mounts the other file systems, things get confused when a mount of
an already mounted file system is attempted.  (Symptom of confusion: when you
do a 'df', the file system which was doubly mounted appears with no name, as
in:

	Filesystem    kbytes    used   avail capacity  Mounted on
	/dev/hp0a       7653    6336     551    92%    /
	/dev/hp0e     150099   46453   88636    34%    /guest
>	/dev/hp0h     142172   76068   51887    59%    
	/dev/hp1g      38639   23865   10910    69%    /uts
	/dev/hp0f     150799  119650   16069    88%    /work
)

So the question is: how does one reliably unmount all file systems so that
the reboot doesn't foul things up?


-- 
kral		408/647-6112		...amdahl!drivax!braun
"Dream lightyears...    Challenge miles...    Walk in steps"
DISCLAIMER: If DRI knew I was saying this stuff, they would shut me d~-~oxx