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