Newbie Question About System Update
Bill Moran
wmoran at potentialtech.com
Tue Apr 19 13:32:39 PDT 2005
Chuck Swiger <cswiger at 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.
--
Bill Moran
Potential Technologies
http://www.potentialtech.com
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