root@desktix / # cat /etc/apt/preferences 
// main grml-repository:
Package: *
Pin: origin deb.grml.org
Pin-Priority: 906

// fallback grml-repository:
Package: *
Pin: origin grml.org
Pin-Priority: 905


// ubuntu's packages:
Package: *
Pin: origin archive.ubuntu.com
Pin-Priority: 910