ubuntu又双叕更新啦！安装好ubuntu双系统或者ubuntu虚拟机之后，默认的软件更新源是国外的，在国内使用速度很慢，用"apt install"安装软件时各种网络问题层出不穷，因此我们需要更换成国内的源，这样才能正常安装和更新软件。
首先将我们的原来的软件源另存起来备份：
sudo cp -v /etc/apt/sources.list /etc/apt/sources.list.backup终端执行chmod命令更改文件权限使软件源文件可编辑：
sudo chmod 777 /etc/apt/sources.list之后通过gedit命令编辑软件源：
sudo gedit /etc/apt/sources.list然后将下面任意一个源复制进去保存就好了：
阿里云源：
deb http://mirrors.aliyun.com/ubuntu/ eoan main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ eoan-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ eoan-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ eoan-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ eoan-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-backports main restricted universe multiverse清华源：
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse修改完软件源后，更新软件列表和软件：
sudo apt update
sudo apt upgrade注意：“eoan”为ubuntu版本名！“eoan”代表ubuntu19.10，“xenial”代表ubuntu16.04，“bionic”代表ubuntu18.04，“disco”代表ubuntu19.04，如果自己的版本不再所描述的上面，可以通过查看，并更改相应位置就ok了！
lsb_release -c