ubuntu20.04 清华源 update 报证书错误

换成清华源后，

https://mirror.tuna.tsinghua.edu.cn/help/ubuntu/

 

sudo  apt update

报证书错误，

Certificate verification failed: The certificate is NOT trusted. The .....

将所有https改为http

然后执行：

audo apt install ca-certificates

然后再改回来https，再update即可。