apt update时出现证书相关问题，可以关闭apt验证

vi /etc/apt/apt.conf.d/99disable-signature-verification 

添加以下内容：

Acquire::AllowInsecureRepositories "true";

Acquire::AllowDowngradeToInsecureRepositories "true";

Acquire::AllowUnauthenticated "true";

参考链接：

apt-secure(8) — apt — Debian unstable — Debian Manpages