If you’ve ever rebooted a machine and NTP refused to sync because the clock drifted too far, you’ve hit the panic threshold. By default, ntpd will exit if the offset exceeds 1000 seconds.

The Fix

Add this to /etc/ntp.conf:

tinker panic 0

Setting panic 0 disables the panic threshold entirely, allowing ntpd to correct any offset regardless of size.

When Is This Useful?

• Machines that have been powered off for a long time (e.g., home servers, lab equipment)
• VMs that resume from a suspended state with a stale clock
• Systems without a working RTC battery
• FreeBSD jails or containers that inherit a drifted host clock

Alternative: One-Time Force Sync

If you don’t want to permanently disable the panic threshold, you can do a one-time force sync with:

ntpd -gq

The -g flag allows the first adjustment to be any size, and -q makes ntpd set the time and exit.