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NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | AVAILABILITY | COLOPHON |
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
2020-08-13. (At that time, the date of the most recent commit that
was found in the repository was 2020-08-12.) If you discover any
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(which is not part of the original manual page), send a mail to
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util-linux August 2018 ADJTIME_CONFIG(5)