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备份一下/etc/apt/sources.list
cp /etc/apt/sources.list /etc/apt/sources.list.bak
vim /etc/apt/sources.list添加一下内容
deb http://mirrors.163.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ bionic-backports main restricted universe multiverse
保存退出
sudo apt-get update
sudo apt-get upgrade详细的不多说，按着操作就ok，当然不止这一种方式，也有界面的操作方式，懒得截图，就不贴了
下面时Ubuntu18.04的命令 ubuntu16.04下在系统设置里边查找update&software这一选项做更改，各个版本的系统都有
sudo update-manager -c -d