加快Ubuntu和CentOS软件下载速度。

Ubuntu

备份源配置文件：

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

使用vim或gedit编辑source.list，用下面内容替换原有内容：

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse

# 预发布软件源，不建议启用
# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse

更新软件包缓存，使配置文件生效：

sudo apt-get update

CentOS

# 清华源
sudo sed -e 's|^mirrorlist=|#mirrorlist=|g' \
         -e 's|^#baseurl=http://mirror.centos.org|baseurl=https://mirrors.tuna.tsinghua.edu.cn|g' \
         -i.bak \
         /etc/yum.repos.d/CentOS-*.repo
# 阿里云
sudo sed -e 's|^mirrorlist=|#mirrorlist=|g' \
         -e 's|^#baseurl=http://mirror.centos.org|baseurl=https://mirrors.aliyun.com|g' \
         -i.bak \
         /etc/yum.repos.d/CentOS-*.repo
# 更新软件包缓存，使配置文件生效
sudo yum makecache

参考链接：
https://mirrors.tuna.tsinghua.edu.cn/help/ubuntu/
https://blog.csdn.net/xiangxianghehe/article/details/105688062
https://mirror.tuna.tsinghua.edu.cn/help/centos/