Ubuntu 切换清华镜像软件源遇到的问题

问题:
certificate verification failed: The certificate is NOT trusted ...... as follows.

解决方法:

• 方法一:

将清华Ubuntu对应版本的软件源里的https替换成http即可, https是加密传输, 需要证书认证, 因此去掉s.

• 方法二:

sudo apt install apt-transport-https