Date: Tue, 19 Apr 2005 22:45:22 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: Bill Moran <wmoran@potentialtech.com> Cc: freebsd-stable@freebsd.org Subject: Re: Newbie Question About System Update Message-ID: <20050419204522.GA28137@falcon.midgard.homeip.net> 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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On Tue, Apr 19, 2005 at 04:32:37PM -0400, Bill Moran wrote: > 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. > > Apparenlty, nobody who is claiming this has _tried_ it. Try it yourself > and see. You can _not_ replace programs that have their Text section > in use (i.e. the code) because the demand pager has that area of the > file locked. You apparently cannot modify a program that is in use. What you *can* do is delete it and create a new file with the same name. Try using 'cp -f' instead of plain 'cp'. (Or use the install(1) utility, which is what installworld normally uses, which also unlinks the old file before creating the new.) -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se
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