Първо във /etc/apt създавате файл preferences след това в него добавяте следните редове:
Package: *
Pin: release o=Debian,a=stable
Pin-Priority: 500
Package: flashplugin-nonfree
Pin: release o=Debian,a=stable
Pin-Priority: -1
Package: empty-expect
Pin: release o=Backports.org archive,a=etch-backports
Pin-Priority: 500
Package: flashplugin-nonfree
Pin: release o=Backports.org ...