How to disable ipv6 ?

[Schneck Dennis CIS SDE]

Hello,
I use: Debian 6 PPC 64bit on IBM Power7 (debian-6.0.2.1-powerpc-DVD-1.iso).
I try some information from different people, but ipv6 is still active.
Is I possible to disable it at boot with yaboot in the /etc/yaboot.conf ?
Thanks