adjtime_config
ADJTIME_CONFIG(5) File formats ADJTIME_CONFIG(5)
NAME
adjtime_config - information about hardware clock setting and drift factor
SYNOPSIS
/etc/adjtime
DESCRIPTION
The file /etc/adjtime contains descriptive information about the hardware mode clock setting and clock drift factor. The file is read and write by hwclock(8); and read by programs
like rtcwake to get RTC time mode.
The file is usually located in /etc, but tools like hwclock(8) or rtcwake(8) can use alternative location by command line options if write access to /etc is unwanted. The default
clock mode is "UTC" if the file is missing.
The Hardware Clock is usually not very accurate. However, much of its inaccuracy is completely predictable - it gains or loses the same amount of time every day. This is called
systematic drift. The util hwclock(8) keeps the file /etc/adjtime, that keeps some historical information. For more details see "The Adjust Function" and "The Adjtime File" sections
from hwclock(8) man page.
The adjtime file is formatted in ASCII.
First line
Three numbers, separated by blanks:
drift factor
the systematic drift rate in seconds per day (floating point decimal)
last adjust time
the resulting number of seconds since 1969 UTC of most recent adjustment or calibration (decimal integer)
adjustment status
zero (for compatibility with clock(8)) as a floating point decimal
Second line
last calibration time
The resulting number of seconds since 1969 UTC of most recent calibration. Zero if there has been no calibration yet or it is known that any previous calibration is moot (for
example, because the Hardware Clock has been found, since that calibration, not to contain a valid time). This is a decimal integer.
Third line
clock mode
Supported values are UTC or LOCAL. Tells whether the Hardware Clock is set to Coordinated Universal Time or local time. You can always override this value with options on the
hwclock(8) command line.
FILES
/etc/adjtime
SEE ALSO
hwclock(8), rtcwake(8)
REPORTING BUGS
For bug reports, use the issue tracker <https://github.com/util-linux/util-linux/issues>.
AVAILABILITY
adjtime_config is part of the util-linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>.
util-linux 2.41 2025-02-26 ADJTIME_CONFIG(5)