/etc/apt/sources.list 의 앞부분에 추가

deb mirror://mirrors.ubuntu.com/mirrors.txt precise main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-updates main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-backports main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt precise-security main restricted universe multiverse

* http://askubuntu.com/questions/39922/how-do-you-select-the-fastest-mirror-from-the-command-line

또는

sed -i s,http://archive.ubuntu.com,http://kr.archive.ubuntu.com,g /etc/apt/sources.list