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To: wmoran@potentialtech.com
From: Warner Losh <imp@bsdimp.com>
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cc: freebsd-stable@freebsd.org
Subject: Re: Newbie Question About System Update
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From: Bill Moran <wmoran@potentialtech.com>
Subject: Re: Newbie Question About System Update
Date: Tue, 19 Apr 2005 16:32:37 -0400

> Chuck Swiger <cswiger@mac.com> wrote:
> > Bill Moran wrote:
> > > The system can not replace programs that are in use,
> > 
> > This is generally not the case.  Unix lets you continue to access a file after 
> > it has been deleted, so long as the process hangs on to a file descriptor. 
> > This lets you replace programs in use, without running into the same problems 
> > that platforms like Windows have.
> 
> What you say?:
> 
> bash-2.05b$ su
> Password:
> bolivia# cp /usr/sbin/cron /home/wmoran/.
> bolivia# cp /home/wmoran/cron /usr/sbin/.
> cp: /usr/sbin/./cron: Text file busy
> bolivia# 

mv /usr/sbin/cron /usr/sbin/cron-
cp /blah/cron /usr/sbin/cron

install does this behind the scenes. 

Warner