10.8 How do I override a file installed by a package, so that a different version can be used instead?
Suppose a sysadmin or local user wishes to use a program
"login-local" rather than the program "login" provided by
Overwrite /bin/login with login-local.
The package management system will not know about this change, and will simply
overwrite your custom /bin/login whenever login (or
any package that provides /bin/login) is installed or updated.
Details are given in the manual page