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NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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ADJTIME_CONFIG(5) File formats ADJTIME_CONFIG(5)
adjtime_config - 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(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.
/etc/adjtime
hwclock(8), rtcwake(8)
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
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/>. 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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2025-08-11. (At that time, the date of the most recent commit that
was found in the repository was 2025-08-05.) 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 [email protected]
util-linux 2.42-start-521-ec46 2025-01-16 ADJTIME_CONFIG(5)
Pages that refer to this page: hwclock(8), rtcwake(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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