I want to using command cp to copy a file, last time i am using rhle3, i can use command cp -f to copy a file without askking me "the files is existing,do you want to overwrite". Now i am using rhle4 than i dont want system to prompt asking me want to overwrite the same files or not.I want to overwrite the file, i dont want system prompt to asking me again.

Thank you.

Make sure cp isn't aliased on one or the other machine - run this command on both:
Probably on one machine has cp aliased to "cp -i". You need to find where the alias is set and comment out / delete that alias. Typical places where aliases are set:

• ~/.bashrc
• ~/.bash_profile
• ~/.profile
• ~/.bash_aliases ~/.aliases or something similar.

Assuming you're using bash as your shell the first three will be checked when you start a log in shell. Often aliases are split out into a separate file which is called from one of the first three files, hence the name of an aliases file if present is not certain - it depends what the author of the main file decided would be nice.

A quick way to try to find the alias:

Indeed on RHEL4 cp is aliased to "cp -i" by default and only for root. After checking as suggested by matthewg42, you have the choice to remove the alias or escape it by preceding the command with a backslash