CP command with more options

Why not put a delete line in the script just before the copy? The files should be on backup tape the night before if anything crashes + you have the file in their original location if the script fails between the delete of the old and the copy ofthe new.

cp -r --remove-destination /home/* /mnt/backup

or

cp -r --reply=yes /home/* /mnt/backup

cp --help will give you a complete list of options

Use one of the archive type commands like tar or cpio.
tar will overwrite the backup each time it is run
tar -cvf /mnt/backup/my_backup.tar /home

Honestly I dont understand why your attempts have not worked. At the command line try typing:
cp -fR /home/* /mnt/backup. If this doesn't work I'd try adding the --remove-destination flag like this

cp -R --remove-destination /home/* /mnt/backup. Again, I believe all of these have been offered as possible solutions. None of these work? Try adding the --reply=yes flag and see if that works. It will basically reply "yes" to any prompt that is given, in effect giving permission to overwrite existing files in /mnt/backup.

you are running it as root?

see if your distro allows

cp -af

-a == pdR / preserve no deference (don't follow symlinks just create a new symlink) and Recursive (but allow for fifo or /dev/null type files)

and also try puting the command as this

\cp -af /home /mnt/backup

the \ means to use the command without any modifications from the environment... or as I understand it to mean..

so if someplace the CP command is set to use "interactive" mode by default, then using the \will negate that setting and use the command straight again.

You'd be surprised where that little \ can come in handy by the way. It solved a sendmail on the command line problem we'd had sending email alerts from our solaris boxes.. by escapingthe command, the command line usage would then correctly allow other switches that weren't working without the \ before a sendmail command line, line.