登錄root用戶
su
#先備份原來的源列表文件
mv /etc/apt/sources.list /etc/apt/sourses.list.backup
#新建源列表文件
vim /etc/apt/sources.list
#加入源地址（推薦用阿里雲源）
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
#更新軟件列表
sudo apt-get update
#更新軟件（把已安裝的軟件與剛刷新的軟件列表中的版本進行對比，如果發現已安裝的軟件版本太低，就會提示更新）
sudo apt-get upgrade