Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!gatech!cuae2!ltuxa!ttrdc!levy
From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.unix-wizards
Subject: Re: ATT 3b2 firmware password
Message-ID: <1246@ttrdc.UUCP>
Date: Wed, 15-Oct-86 00:27:47 EDT
Article-I.D.: ttrdc.1246
Posted: Wed Oct 15 00:27:47 1986
Date-Received: Wed, 15-Oct-86 21:58:03 EDT
References: <305@pinney.munsell.UUCP> <3900001@snail> <146@opusys.UUCP>
Organization: AT&T, Computer Systems Division, Skokie, IL
Lines: 32

In article <146@opusys.UUCP>, jk@opusys.UUCP (John Kullmann) writes:
>In article <3900001@snail> carroll@snail.CS.UIUC.EDU writes:
>>or yank the power cord (which
>>is pretty much guaranteed to trash the file system). 
>Are you telling me that if I type 'sync' (and there are no
>other users) and wait until the disk stops thrashing and then
>pull the plug the file system will be trashed?!?!??!?!?
>I'd like to know what extra work was done to the 3B2 to get
>this effect.

Indeed, if you 'sync', and nothing else is running (uucp, etc.) which
has a file open for writing, you have a good chance of getting away
scot-free if you yank the 3B2's cord.  When the system is powered back
on, it will go through a fsck for each file system (since each file
system with write access is marked "dirty" when mounted and then marked
"clean" when properly dismounted, and the startup shell script runs a
program which checks for "dirty" file systems before mounting them).  But
if nothing had made a change in the file system since the last sync action
finished (sync actually only schedules a file system update) then the
file system state will be set to okay ("clean") and that file system will
then be mounted.

Even if some programs have files open for writing when the power is killed,
it is likely that any damage done will be limited to those files.
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
 --------------------------------   Path: ..!{akgua,homxb,ihnp4,ltuxa,mvuxa,
	   go for it!  			allegra,ulysses,vax135}!ttrdc!levy