Date: Tue, 19 Apr 2005 15:39:13 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: Bill Moran <wmoran@potentialtech.com> Cc: freebsd-stable@freebsd.org Subject: Re: Newbie Question About System Update Message-ID: <20050419203913.GB50313@dan.emsphone.com> In-Reply-To: <20050419163237.76a99373.wmoran@potentialtech.com> References: <426447F8.5090209@charter.net> <200504191317.j3JDH76H001458@drjekyll.mkbuelow.net> <20050419120053.6ad17df1.wmoran@potentialtech.com> <42655B8E.5020603@mac.com> <20050419163237.76a99373.wmoran@potentialtech.com>
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In the last episode (Apr 19), Bill Moran said: > 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# > > Notice that /usr/sbin/cron is in use (because my system is running > normally) I can copy _from_ that file, but I can not overwrite it. What you can do, however, is: create the new file under a temporary name, delete the original, and rename the temp file to the orignal's name, which is what /usr/bin/install does. I've done many installworlds on running systems without problems. -- Dan Nelson dnelson@allantgroup.com
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