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


initialize system time


#include <sys/types.h>
#include <sys/systm.h>
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 obtained from the root file system, as given in base. How the base value is obtained will vary depending on the root file system type. The heuristics used include:
  • If the battery-backed clock has a valid time, it is used.
  • If the battery-backed clock does not have a valid time, the time provided in base 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:
  • The battery-backed clock's time appears nonsensical.


resettodr(9), time(9)


On many systems, inittodr() has to convert from a time expressed in terms of year, month, day, hours, minutes, and seconds to time, expressed in seconds. Many of the implementations could share code, but do not.
Each system's heuristics for picking the correct time are slightly different.
The FreeBSD implementation should do a better job of validating the time provided in base when the battery-backed clock is unusable. Currently it unconditionally sets the system clock to this value.
March 22, 1997 Debian