su without password

Google returns a lot of meaningful results for “sudo without password” and “ssh without password.” I don’t know why googling “su without password” gives no useful info.

To allow a user to become root with su without entering the password, edit /etc/pam.d/su.

For example, in Gentoo (should be the same or similar in other distros) uncommenting the following line allows users in group wheel to su without password:

auth sufficient pam_wheel.so use_uid trust