更新软件源

    1 首先备份源列表:
        sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup
    2 而后用gedit或其他编辑器打开:
        sudo gedit /etc/apt/sources.list
    3 更新源：

        deb http://mirrors.sohu.com/ubuntu/ oneiric main restricted universe multiverse
        deb http://mirrors.sohu.com/ubuntu/ oneiric-security main restricted universe multiverse
        deb http://mirrors.sohu.com/ubuntu/ oneiric-updates main restricted universe multiverse
        deb http://mirrors.sohu.com/ubuntu/ oneiric-proposed main restricted universe multiverse
        deb http://mirrors.sohu.com/ubuntu/ oneiric-backports main restricted universe multiverse
        deb-src http://mirrors.sohu.com/ubuntu/ oneiric main restricted universe multiverse
        deb-src http://mirrors.sohu.com/ubuntu/ oneiric-security main restricted universe multiverse
        deb-src http://mirrors.sohu.com/ubuntu/ oneiric-updates main restricted universe multiverse
        deb-src http://mirrors.sohu.com/ubuntu/ oneiric-proposed main restricted universe multiverse
        deb-src http://mirrors.sohu.com/ubuntu/ oneiric-backports main restricted universe multiverse

　4 刷新列表：

        sudo apt-get update