ADJTIMEXCONFIG(8) System Manager's Manual ADJTIMEXCONFIG(8)NAME
adjtimexconfig - find kernel clock variables and save for reboots
SYNOPSIS
/sbin/adjtimexconfig
DESCRIPTION
This script uses adjtimex(8) to find values for the kernel variables tick and frequency that will make the system clock approximately agree
with the CMOS clock. It then saves these values in the configuration file /etc/default/adjtimex so the settings will be restored on every
boot, when /etc/init.d/adjtimex runs.
adjtimexconfig uses the drift rate recorded in /etc/adjtime to adjust the times it reads from the CMOS clock. If you find the CMOS clock
has a systematic drift, read the clock(8) or hwclock(8) manual page, modify /etc/adjtime as required, and run adjtimexconfig again.
AUTHOR
Michael Meskes <meskes@debian.org>.
FILES
/etc/default/adjtimex
/etc/init.d/adjtimex
SEE ALSO adjtimex(8), clock(8), hwclock(8), ntpd(8)
April 27, 2003 ADJTIMEXCONFIG(8)
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ADJTIMEX(2) Linux Programmer's Manual ADJTIMEX(2)NAME
adjtimex - tune kernel clock
SYNOPSIS
#include <sys/timex.h>
int adjtimex(struct timex *buf);
DESCRIPTION
Linux uses David L. Mills' clock adjustment algorithm (see RFC 1305). The system call adjtimex() reads and optionally sets adjustment
parameters for this algorithm. It takes a pointer to a timex structure, updates kernel parameters from field values, and returns the same
structure with current kernel values. This structure is declared as follows:
struct timex {
int modes; /* mode selector */
long offset; /* time offset (usec) */
long freq; /* frequency offset (scaled ppm) */
long maxerror; /* maximum error (usec) */
long esterror; /* estimated error (usec) */
int status; /* clock command/status */
long constant; /* pll time constant */
long precision; /* clock precision (usec) (read-only) */
long tolerance; /* clock frequency tolerance (ppm)
(read-only) */
struct timeval time; /* current time (read-only) */
long tick; /* usecs between clock ticks */
};
The modes field determines which parameters, if any, to set. It may contain a bitwise-or combination of zero or more of the following
bits:
#define ADJ_OFFSET 0x0001 /* time offset */
#define ADJ_FREQUENCY 0x0002 /* frequency offset */
#define ADJ_MAXERROR 0x0004 /* maximum time error */
#define ADJ_ESTERROR 0x0008 /* estimated time error */
#define ADJ_STATUS 0x0010 /* clock status */
#define ADJ_TIMECONST 0x0020 /* pll time constant */
#define ADJ_TICK 0x4000 /* tick value */
#define ADJ_OFFSET_SINGLESHOT 0x8001 /* old-fashioned adjtime() */
Ordinary users are restricted to a zero value for mode. Only the superuser may set any parameters.
RETURN VALUE
On success, adjtimex() returns the clock state:
#define TIME_OK 0 /* clock synchronized */
#define TIME_INS 1 /* insert leap second */
#define TIME_DEL 2 /* delete leap second */
#define TIME_OOP 3 /* leap second in progress */
#define TIME_WAIT 4 /* leap second has occurred */
#define TIME_BAD 5 /* clock not synchronized */
On failure, adjtimex() returns -1 and sets errno.
ERRORS
EFAULT buf does not point to writable memory.
EINVAL An attempt is made to set buf.offset to a value outside the range -131071 to +131071, or to set buf.status to a value other than
those listed above, or to set buf.tick to a value outside the range 900000/HZ to 1100000/HZ, where HZ is the system timer interrupt
frequency.
EPERM buf.mode is nonzero and the caller does not have sufficient privilege. Under Linux the CAP_SYS_TIME capability is required.
CONFORMING TO
adjtimex() is Linux-specific and should not be used in programs intended to be portable. See adjtime(3) for a more portable, but less
flexible, method of adjusting the system clock.
SEE ALSO settimeofday(2), adjtime(3), capabilities(7), time(7)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2004-05-27 ADJTIMEX(2)