尝试过更新很多源，比如aliyun的源，清华的源都不行，都会报404如：
root@149e8cb9cd56:/usr/local/var/bin# apt-get 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
Err:4 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal Release
Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown. Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Err:5 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-updates Release
Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown. Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Err:6 https://mirrors.tuna.tsinghua.edu.cn/ubuntu focal-backports Release
Certificate verification failed: The certificate is NOT trusted. The certificate issuer is unknown. Could not handshake: Error in the certificate verification. [IP: 101.6.15.130 443]
Get:7 http://security.ubuntu.com/ubuntu focal-security InRelease [114 kB]
Ign:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages
Ign:10 http://security.ubuntu.com/ubuntu focal-security/universe arm64 Packages
Ign:11 http://security.ubuntu.com/ubuntu focal-security/main arm64 Packages
Ign:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages
Ign:10 http://security.ubuntu.com/ubuntu focal-security/universe arm64 Packages
Ign:11 http://security.ubuntu.com/ubuntu focal-security/main arm64 Packages
Ign:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages
Ign:10 http://security.ubuntu.com/ubuntu focal-security/universe arm64 Packages
Ign:11 http://security.ubuntu.com/ubuntu focal-security/main arm64 Packages
Ign:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages
Ign:10 http://security.ubuntu.com/ubuntu focal-security/universe arm64 Packages
Ign:11 http://security.ubuntu.com/ubuntu focal-security/main arm64 Packages
Ign:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages
Ign:10 http://security.ubuntu.com/ubuntu focal-security/universe arm64 Packages
Ign:11 http://security.ubuntu.com/ubuntu focal-security/main arm64 Packages
Err:8 http://security.ubuntu.com/ubuntu focal-security/restricted arm64 Packages
404 Not Found [IP: 91.189.91.83 80]
Ign:9 http://security.ubuntu.com/ubuntu focal-security/multiverse arm64 Packages解决方案
运行下面命令
mv /etc/apt/sources.list /etc/apt/sources.list.back
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy main restricted > /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy multiverse universe >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-updates main restricted >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-updates multiverse universe >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-backports main restricted >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-backports multiverse universe >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-security main restricted >> /etc/apt/sources.list
echo deb http://old-releases.ubuntu.com/ubuntu/ groovy-security multiverse universe >> /etc/apt/sources.list
文章来源：https://uudwc.com/A/8d1qm
再执行
apt-get update
apt-get upgrade
就可以了文章来源地址https://uudwc.com/A/8d1qm
