1ADJTIME_CONFIG(5) File Formats ADJTIME_CONFIG(5)
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6 adjtime - information about hardware clock setting and drift factor
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9 /etc/adjtime
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12 The file /etc/adjtime contains descriptive information about the hard‐
13 ware mode clock setting and clock drift factor. The file is read and
14 write by hwclock; and read by programs like rtcwake to get RTC time
15 mode.
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17 The file is usually located in /etc, but tools like hwclock(8) or
18 rtcwake(8) allow to use alternative location by command line options if
19 write access to /etc is unwanted. The default clock mode is "UTC" if
20 the file is missing.
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22 The Hardware Clock is usually not very accurate. However, much of its
23 inaccuracy is completely predictable - it gains or loses the same
24 amount of time every day. This is called systematic drift. The util
25 hwclock keeps the file /etc/adjtime, that keeps some historical infor‐
26 mation. For more details see "The Adjust Function" and "The Adjtime
27 File" sections from hwclock(8) man page.
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29 The format of the adjtime file is, in ASCII.
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32 First line
33 Three numbers, separated by blanks:
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35 drift factor
36 the systematic drift rate in seconds per day (floating point
37 decimal)
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39 last adjust time
40 the resulting number of seconds since 1969 UTC of most
41 recent adjustment or calibration (decimal integer)
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43 adjustment status
44 zero (for compatibility with clock(8)) as a floating point deci‐
45 mal
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48 Second line
49 last calibration time
50 The resulting number of seconds since 1969 UTC of most recent
51 calibration. Zero if there has been no calibration yet or it is
52 known that any previous calibration is moot (for example,
53 because the Hardware Clock has been found, since that calibra‐
54 tion, not to contain a valid time). This is a decimal integer.
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57 Third line
58 clock mode
59 Supported values are "UTC" or "LOCAL". Tells whether the Hard‐
60 ware Clock is set to Coordinated Universal Time or local time.
61 You can always override this value with options on the hwclock
62 command line.
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66 /etc/adjtime
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69 hwclock(8), rtcwake(8)
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72 This man page is part of the util-linux package and is available from
73 https://www.kernel.org/pub/linux/utils/util-linux/.
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77util-linux August 2018 ADJTIME_CONFIG(5)