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NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | AVAILABILITY | COLOPHON |
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ADJTIME_CONFIG(5) File Formats ADJTIME_CONFIG(5)
adjtime - information about hardware clock setting and drift
factor
/etc/adjtime
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 Adjust
Function" and "The Adjtime File" sections from hwclock(8) man
page.
The format of the adjtime file is, 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 command line.
/etc/adjtime
hwclock(8), rtcwake(8)
This man page is part of the util-linux package and is available
from https://www.kernel.org/pub/linux/utils/util-linux/.
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
have a bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-12-17.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
util-linux August 2018 ADJTIME_CONFIG(5)
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