adjtime_config(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | AVAILABILITY | COLOPHON

ADJTIME_CONFIG(5)             File Formats             ADJTIME_CONFIG(5)

NAME         top

       adjtime - information about hardware clock setting and drift
       factor

SYNOPSIS         top

       /etc/adjtime

DESCRIPTION         top

       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.

FILES         top

       /etc/adjtime

SEE ALSO         top

       hwclock(8), rtcwake(8)

AVAILABILITY         top

       This man page is part of the util-linux package and is available
       from https://www.kernel.org/pub/linux/utils/util-linux/.

COLOPHON         top

       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
       2021-03-21.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-03-19.)  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)