iso：Ubuntu20.04
1.系统设置-->软件和更新-->更新，将“自动检查更新”和“有新版本时通知我”设置为“从不“，关闭对话框完成设置。
2.修改配置文件
修改配置文件/etc/apt/apt.conf.d/10periodic
b305@b305:~$cat /etc/apt/apt.conf.d/10periodic
APT : :Periodic: : Update-Package-Lists "1";
APT : :Periodic: : Download-Upgradeable-Packages "0";
APT : :Periodic: :AutocleanInterval "0";
APT : :Periodic: :Unattended-Upgrade "0";更改为图片所示：
