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; 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 keeps the file /etc/adjtime, that keeps
some historical information. For more details see "The AdjustFunction" and "The Adjtime File" sections from hwclock(8) man
The format of the adjtime file is, in ASCII.
Three numbers, separated by blanks:
the systematic drift rate in seconds per day (floating
last adjust time
the resulting number of seconds since 1969 UTC of most
recent adjustment or calibration (decimal integer)
zero (for compatibility with clock(8)) as a floating point
Second linelast 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 lineclock 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 command line.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found
at ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you
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2021-03-21. (At that time, the date of the most recent commit
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util-linux August 2018 ADJTIME_CONFIG(5)