Manual browser: inittodr(9)

INITTODR(9) Kernel Developer's Manual INITTODR(9)


inittodrinitialize system time


inittodr(time_t base);


The inittodr() function determines the time and sets the system clock. It tries to pick the correct time using a set of heuristics that examine the system's battery-backed clock and the time reported by the file system, as given in base. Those heuristics include:
  • If the battery-backed clock has a valid time, and is not significantly behind the time provided by base, it is used.
  • If the battery-backed clock does not have a valid time, or is significantly behind the time provided in base, and the time provided in base is within reason, base is used as the current time.
  • If the battery-backed clock appears invalid, and base appears non-sensical or was not provided (was given as zero), an arbitrary base (typically some time within the same year that the kernel was last updated) will be used.

Once a system time has been determined, it is stored in the time variable.


The inittodr() function prints diagnostic messages if it has trouble figuring out the system time. Conditions that can cause diagnostic messages to be printed include:
  • There is no battery-backed clock present on the system.
  • The battery-backed clock's time appears nonsensical.
  • The base time appears nonsensical.
  • The base time and the battery-backed clock's time differ by a large amount.


Some systems use heuristics for picking the correct time that are slightly different.
September 6, 2006 NetBSD 7.0