1.备份源列表

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

2.编辑 sources.list

sudo vim /etc/apt/sources.list

查找源文件

查看系统的代号：lsb_release -a

Ubuntu20.04 LTS更新阿里源_vim

到阿里源下查找 focal 是否存在: http://mirrors.aliyun.com/ubuntu/dists/

然后以下面的为模板，把'TODO'的地方换成上面的Codename

deb http://mirrors.aliyun.com/ubuntu/ TODO main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-backports main restricted universe multiverse

##替换后阿里云源

deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse

然后保存 sources.list

3.更新列表

sudo apt-get update
sudo apt-get upgrade （注意：这个命令是更新所有软件的意思）