1,最好用系统自带的apt源,我用163的源升级没有成功
tao@tao-desktop:~$ grep -v ^# /etc/apt/sources.list|grep -v ^$
deb http://cn.archive.ubuntu.com/ubuntu/ precise main restricted
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ precise-updates main restricted
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise-updates main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ precise universe
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise universe
deb http://cn.archive.ubuntu.com/ubuntu/ precise-updates universe
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise-updates universe
deb http://cn.archive.ubuntu.com/ubuntu/ precise multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ precise-updates multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu/ precise-updates multiverse
deb http://security.ubuntu.com/ubuntu precise-security main restricted
deb-src http://security.ubuntu.com/ubuntu precise-security main restricted
deb http://security.ubuntu.com/ubuntu precise-security universe
deb-src http://security.ubuntu.com/ubuntu precise-security universe
deb http://security.ubuntu.com/ubuntu precise-security multiverse
deb-src http://security.ubuntu.com/ubuntu precise-security multiverse
deb http://archive.canonical.com/ precise partner
2,开始更新
tao@tao-desktop:~$ sudo update-manager -d
弹出更新管理器,发现有新的版本12.04LTS,双击升级即可