systemd-time-wait-sync.service, systemd-time-wait-sync — Wait Until Kernel Time Synchronized
systemd-time-wait-sync is a system service that delays the start of units that depend on
time-sync.target until the system time has been synchronized with an accurate time source by
systemd-timesyncd.service notifies on successful synchronization.
systemd-time-wait-sync also tries to detect when the kernel marks the time as synchronized,
but this detection is not reliable and is intended only as a fallback for other servies that can be used to
synchronize time (e.g., ntpd, chronyd).
The presence of this file indicates to this service that the system clock has been synchronized.