查看系统版本和代号
lsb_release -a
替换apt源步骤
cd /etc/apt/
sudo mv sources.list sources.list.bak
sudo gedit sources.list
如系统为ubuntu20.04代号focal,用中科院的
deb https://mirrors.ustc.edu.cn/ubuntu/ focal main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-security main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-security main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
## Not recommended
# deb https://mirrors.ustc.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
阿里云镜像源：https://mirrors.aliyun.com/
中科院镜像源：https://mirrors.ustc.edu.cn/repogen/
搜狐开源镜像：http://mirrors.sohu.com/
网易开源镜像：http://mirrors.163.com/