adjtime_config(5) — Linux manual page


ADJTIME_CONFIG(5)             File formats             ADJTIME_CONFIG(5)

NAME         top

       adjtime_config - information about hardware clock setting and
       drift factor

SYNOPSIS         top


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(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

       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

       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

   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

   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.

FILES         top


SEE ALSO         top

       hwclock(8), rtcwake(8)

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       adjtime_config is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨⟩. If you have
       a bug report for this manual page, send it to This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2024-06-14. (At that time, the date of the most recent commit
       that was found in the repository was 2024-06-10.) 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

util-linux 2.39.594-1e0ad      2023-07-19              ADJTIME_CONFIG(5)

Pages that refer to this page: hwclock(8)rtcwake(8)