It's upset because the same entries appears twice in sources.list or sources.list.d/*. Remove the duplicates. Glancing at the paste, the problem appears to be the partners repo. Here is a complete sources.list: # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. # ## updates -- Major bug fix updates produced after the final release ## of the distribution. ## ## N.B. software from "universe" is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. ## See also http://cyber.com.au/~twb/snarf/vtwb ## ## N.B. software from "backports" may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb mirror://mirrors.ubuntu.com/mirrors.txt precise main universe deb mirror://mirrors.ubuntu.com/mirrors.txt precise-updates main universe #deb mirror://mirrors.ubuntu.com/mirrors.txt precise-backports main universe deb mirror://mirrors.ubuntu.com/mirrors.txt precise-security main universe deb http://mirror.internode.on.net/pub/ubuntu/ubuntu precise main universe deb http://mirror.internode.on.net/pub/ubuntu/ubuntu precise-updates main universe #deb http://mirror.internode.on.net/pub/ubuntu/ubuntu precise-backports main universe deb http://mirror.internode.on.net/pub/ubuntu/ubuntu precise-security main universe