I've just attempted to run sudo apt-get dist-upgrade on my Ubuntu box, but am getting the following error... WARNING: The following packages cannot be authenticated! librdbmspp php5-ioncube-loader sw-libboost-date-time1.49.0 sw-libboost-system1.49.0 sw-libboost-filesystem1.49.0 sw-libboost-program-options1.49.0 sw-libboost-regex1.49.0 sw-libboost-serialization1.49.0 sw-libpoco I've tried running... $ sudo apt-key update $ sudo apt-get update ... as found in this question, but I'm still getting the error. Can anyone help, please? Update on 5th June Repos currently in /etc/apt/sources.list (links broken due to reputation being too low to include more than 2 links)… deb http: //gb.archive.ubuntu.com/ubuntu/ precise main restricted universe multiverse deb http: //gb.archive.ubuntu.com/ubuntu/ precise-updates main restricted universe multiverse deb http: //gb.archive.ubuntu.com/ubuntu precise-security main restricted universe multiverse deb http: //archive.canonical.com/ubuntu precise partner deb-src http://archive.canonical.com/ubuntu precise partner deb http: //security.ubuntu.com/ubuntu precise-security main restricted universe multiverse deb-src http://security.ubuntu.com/ubuntu precise-security main restricted universe multiverse deb http: //autoinstall.plesk.com/ubuntu/PSA_11.5.30 precise all deb http: //autoinstall.plesk.com/debian/SITEBUILDER_11.5.10 all all deb http: //autoinstall.plesk.com/debian/BILLING_11.5.30 all all