更换科大源
方案一：在命令行输入 sudo gedit /etc/apt/sources.list ，打开系统自带源文件。
将文件内源删除，更换为以下科大源：
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
保存文件退出，执行 sudo apt-get update 进行更新。
执行 sudo apt-get upgrade 更新相关工具集，一定要更新，否则会出现工具集版本不匹配的问题。
方案二：
直接在ubuntu内找到软件和更新，进行如下配置；
将下载自，里面的源地址更改成科大网站，关闭，等待更新完成。