Linux系统安装完后软件源一般都是国外服务器，在国内特别慢，这时候就需要更换国内的镜像源。如163、aliyun 还有各高校镜像源等。记住先备份原始源在更换源，以防以后备用。
一.centos
1.备份：mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2.更换源：下载新的CentOS-Base.repo到/etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
或者 curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
注意http://mirrors.aliyun.com/repo/Centos-7.repo中的7改为自己的Centos版本号，比如Centos 8就是http://mirrors.aliyun.com/repo/Centos-8.repo。
3.运行yum makecache生成缓存
二.ubuntu
1.备份：sudo cp /etc/apt/sources.list /etc/apt/sources_init.list
2.更改文件权限使其可编辑 sudo chmod 777 /etc/apt/source.list
3.更换源 sudo nano /etc/apt/sources.list
使用nano打开文本，删除原来文件里的内容，将下面其中一个源复制进去，然后保存。
阿里源：
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse清华源：
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse4.更新源：sudo apt-get update
5.修复损坏的软件包：sudo apt-get -f install
6.更新软件：sudo apt-get upgrade
三.Debian
1.备份：sudo cp /etc/apt/sources.list /etc/apt/sources.list_bak
2.更换源：将/etc/apt/sources.list文件中 Debian 默认的源地址http://deb.debian.org替换为http://mirrors.ustc.edu.cn（清华源）即可。命令：sudo sed -i 's/deb.debian.org/mirrors.ustc.edu.cn/g' /etc/apt/sources.list
也可以直接编辑/etc/apt/sources.list文件（v）
命令：sudo vi /etc/apt/sources.list 加入如下内容即可
deb http://mirrors.ustc.edu.cn/debian stable main contrib non-free
# deb-src http://mirrors.ustc.edu.cn/debian stable main contrib non-free
deb http://mirrors.ustc.edu.cn/debian stable-updates main contrib non-free
# deb-src http://mirrors.ustc.edu.cn/debian stable-updates main contrib non-free
# deb http://mirrors.ustc.edu.cn/debian stable-proposed-updates main contrib non-free
# deb-src http://mirrors.ustc.edu.cn/debian stable-proposed-updates main contrib non-free敲击i键进入插入模式，组合键ctrl+shift+v将复制内容粘贴至源文件中，敲击esc键进入命令模式，输入:wq!保存并退出。
其他镜像源：
阿里云：http://mirrors.aliyun.com/
搜狐：http://mirrors.sohu.com/
网易：http://mirrors.163.com/
3.更新 sudo apt-get update
