You probably have an alias somewhere, mapping
cp
to
cp -i;
because with the default settings,
cp
won't ask to overwrite. Check your
.bashrc
, your
.profile
etc.
See cp manpage: Only when -i parameter is specified will cp actually prompt before overwriting.
You can check this via the
alias
command:
$ alias
alias cp='cp -i'
alias diff='diff -u'
....
To undefine the alias, use:
$ unalias cp