腾讯云轻量级服务器 ubuntu20.04 安装java报错：
Err:1 http://mirrors.tencentyun.com/ubuntu focal-security/main amd64 libnss3 amd64 2:3.49.1-1ubuntu1.5 404 Not Found [IP: Err:2 http://mirrors.tencentyun.com/ubuntu focal-security/main amd64 openjdk-11-jre-headless amd64 11.0.11+9-0ubuntu2~20.04 404 Not Found Err:3 http://mirrors.tencentyun.com/ubuntu focal-security/main amd64 openjdk-11-jre amd64 11.0.11+9-0ubuntu2~20.04 404 Not Found E: Failed to fetch http://mirrors.tencentyun.com/ubuntu/pool/main/n/nss/libnss3_3.49.1-1ubuntu1.5_amd64.deb 404 Not Found E: Failed to fetch http://mirrors.tencentyun.com/ubuntu/pool/main/o/openjdk-lts/openjdk-11-jre-headless_11.0.11+9-0ubuntu2~20.04_amd64.deb 404 Not Found E: Failed to fetch http://mirrors.tencentyun.com/ubuntu/pool/main/o/openjdk-lts/openjdk-11-jre_11.0.11+9-0ubuntu2~20.04_amd64.deb 404 Not Found E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
错误原因很简单，但搞了半天，算是个教训
解决方案：
sudo apt-get update
