root@master-1:/etc/kubeasz# apt update 
Ign:1 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal InRelease   
Ign:2 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-updates InRelease
Ign:3 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-backports InRelease
Ign:4 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-security InRelease
Err:5 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal Release     
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Err:6 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-updates Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Err:7 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-backports Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Err:8 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-security Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Reading package lists... Done                                       
E: The repository 'https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-updates Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-backports Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-security Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@master-1:/etc/kubeasz# ping www.baidu.com
PING www.wshifen.com (103.235.46.39) 56(84) bytes of data.
64 bytes from 103.235.46.39 (103.235.46.39): icmp_seq=1 ttl=44 time=172 ms
64 bytes from 103.235.46.39 (103.235.46.39): icmp_seq=2 ttl=44 time=173 ms

这是自己的清华源证书出错了 将/etc/apt/sources.list 里面的https改成http即可解决