Newbie Question About System Update

Bill Moran wmoran at
Tue Apr 19 13:32:39 PDT 2005

Chuck Swiger <cswiger at> 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
bolivia# cp /usr/sbin/cron /home/wmoran/.
bolivia# cp /home/wmoran/cron /usr/sbin/.
cp: /usr/sbin/./cron: Text file busy

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

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