Login as www-data apache user in ubuntu

why it is not possible to "sudo su www-data" ?

-Simply, for security reasons

why I may need to login as www-data?

-For testing purposes

-How to do so?

sudo usermod -s /bin/bash www-data




Resources:

• http://askubuntu.com/questions/486346/this-account-is-currently-not-available-error-when-trying-to-ssh
• http://superuser.com/questions/119179/how-can-i-change-shell-in-ubuntu
• http://manpages.ubuntu.com/manpages/hardy/man8/usermod.8.html
• http://manpages.ubuntu.com/manpages/gutsy/man1/chsh.1.html