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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
commit8cb83eee5a58b1fad74c34094ce3afb9e430b5a4 (patch)
treea9b2e7baeca1be40eb734371e3c8b11b02294497 /sys-utils/adjtime_config.5
parentInitial commit. (diff)
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util-linux-upstream.zip
Adding upstream version 2.33.1.upstream/2.33.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.TH ADJTIME_CONFIG 5 "August 2018" "util-linux" "File Formats"
+.SH NAME
+adjtime \- information about hardware clock setting and drift factor
+.SH SYNOPSIS
+.I /etc/adjtime
+.SH DESCRIPTION
+The file
+.B /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.
+.PP
+The file is usually located in /etc, but tools like
+.BR hwclock (8)
+or
+.BR 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.
+.PP
+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 "\fBThe Adjust Function\fR" and "\fBThe Adjtime File\fR" sections from
+.BR hwckock (8)
+man page.
+.PP
+
+The format of the adjtime file is, in ASCII.
+.sp
+.SS First line
+Three numbers, separated by blanks:
+.TP
+.B "drift factor"
+the systematic drift rate in seconds per day (floating point decimal)
+.TP
+.B last adjust time
+the resulting number of seconds since 1969 UTC of most recent adjustment or calibration (decimal integer)
+.TP
+.B "adjustment status"
+zero (for compatibility with clock(8)) as a decimal integer.
+
+.SS Second line
+.TP
+.B "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.
+
+.SS Third line
+.TP
+.B "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.
+
+.SH FILES
+.IR /etc/adjtime
+.SH "SEE ALSO"
+.BR hwclock (8),
+.BR rtcwake (8)
+.SH AVAILABILITY
+This man page is part of the util-linux package and is available from
+https://www.kernel.org/pub/linux/utils/util-linux/.