将Debian下载源同步到本地之后，通过本地资源地址进行apt update操作时提示过期问题：

E: Release file for http://localhost/security/dists/stable/updates/InRelease is expired (invalid since 1d 1h 53min 38s). Updates for this repository will not be applied.

 对于该问题有三种解决方法：

1）通过cron实现定期同步。

2）零时解决方法：

aptitude -o Acquire::Check-Valid-Until=false update  apt-get -o Acquire::Check-Valid-Until=false update

 3）创建文件：/etc/apt/apt.conf.d/10no--check-valid-until，添加内容：

Acquire::Check-Valid-Until "0";

 然后就不再提示过期警告了。

参考：

【1】https://www.bufeihua.cn/p/562249fca47d0b0001b5cc10

【2】http://unix.stackexchange.com/questions/2544/how-to-work-around-release-file-expired-problem-on-a-local-mirror