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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards
Subject: Re: ps problem solved - more stupidity on our part
Message-ID: <1530@umcp-cs.UUCP>
Date: Tue, 10-Sep-85 08:57:10 EDT
Article-I.D.: umcp-cs.1530
Posted: Tue Sep 10 08:57:10 1985
Date-Received: Sat, 14-Sep-85 01:46:04 EDT
References: <845@burl.UUCP> <783@lsuc.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 30

Actually, ``ps'' and other kernel-grubbers should generally be
setgid (not setuid) to a special group that can read the appropriate
files.

I have a question, though: is SysV's /dev/swap somehow different
from 4.xBSD's /dev/drum?  If not, the suggestion given here
(approximately ``ln /dev/fuji /dev/swap'') won't work.

Under 4BSD, /dev/drum is a ``magic'' raw disk device that gives
access to all swap areas, no matter what or where they are.
Internally only, there is also a fake block device.  I quote from
the bottom of /sys/vax/conf.c:

	/*
	 * Swapdev is a fake device implemented
	 * in sw.c used only internally to get to swstrategy.
	 * It cannot be provided to the users, because the
	 * swstrategy routine munches the b_dev and b_blkno entries
	 * before calling the appropriate driver.  This would horribly
	 * confuse, e.g. the hashing routines. Instead, /dev/drum is
	 * provided as a character (raw) device.
	 */

This actually seems like a cleaner way to implement user I/O to
the swap areas, as one need do nothing other than reconfigure the
kernel and edit /etc/fstab to change the swap and paging configuration.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland