ADJTIME_CONFIG(5) File Formats ADJTIME_CONFIG(5)
adjtime - information about hardware clock setting and drift factor
The file /etc/adjtime contains descriptive information about the hard-
ware 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
The file is usually located in /etc, but tools like hwclock(8) or
rtcwake(8) allow to 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 infor-
mation. For more details see "The Adjust Function" and "The Adjtime
File" sections from hwckock(8) man page.
The format of the adjtime file is, in ASCII.
Three numbers, separated by blanks:
the systematic drift rate in seconds per day (floating point
last adjust time
the resulting number of seconds since 1969 UTC of most re-
cent adjustment or calibration (decimal integer)
zero (for compatibility with clock(8)) as a decimal integer.
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, be-
cause the Hardware Clock has been found, since that calibration,
not to contain a valid time). This is a decimal integer.
Supported values are "UTC" or "LOCAL". Tells whether the Hard-
ware Clock is set to Coordinated Universal Time or local time.
You can always override this value with options on the hwclock
This man page is part of the util-linux package and is available from
util-linux August 2018 ADJTIME_CONFIG(5)
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