hwclock: fix spelling, punctuation and formatting mistakes in the man page
Also improve some wordings. Signed-off-by: Benno Schulenberg <bensberg@justemail.net>
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@ -24,16 +24,15 @@ Hardware Clock values based on its drift rate.
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.PP
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Since v2.26 important changes were made to the
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.B \-\-hctosys
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function, the
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function and the
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.B \-\-directisa
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option, and a new option
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.B \-\-update\-drift
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was added. See their respective sections below.
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was added. See their respective descriptions below.
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.
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.SH FUNCTIONS
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The following functions are mutually exclusive, only one can be given at
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a time. If none are given the default is
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.BR \-\-show .
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a time. If none is given, the default is \fB\-\-show\fR.
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.TP
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.B \-\-adjust
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Add or subtract time from the Hardware Clock to account for systematic
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@ -60,9 +59,9 @@ that the year counter in your Hardware Clock contains the number of
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full years since 1952, then the kernel's Hardware Clock epoch value
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must be 1952.
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.sp
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The set function requires using the
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The \fB\%\-\-setepoch\fR function requires using the
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.B \%\-\-epoch
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option.
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option to specify the year.
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.sp
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This epoch value is used whenever
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.B \%hwclock
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@ -124,7 +123,7 @@ function does this based upon the information in the
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.I @ADJTIME_PATH@
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file or the command line arguments
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.BR \%\-\-localtime " and " \-\-utc .
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Note: no daylight saving adjustment is made. See the discussion below under
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Note: no daylight saving adjustment is made. See the discussion below, under
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.BR "LOCAL vs UTC" .
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.sp
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The kernel also keeps a timezone value, the
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@ -154,7 +153,7 @@ This is a good function to use in one of the system startup scripts before the
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file systems are mounted read/write.
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.sp
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This function should never be used on a running system. Jumping system time
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will cause problems, such as, corrupted filesystem timestamps. Also, if
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will cause problems, such as corrupted filesystem timestamps. Also, if
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something has changed the Hardware Clock, like NTP's \%'11\ minute\ mode', then
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.B \%\-\-hctosys
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will set the time incorrectly by including drift compensation.
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@ -231,9 +230,9 @@ changed then a reboot would be required to inform the kernel.
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.BR \-w , \ \-\-systohc
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Set the Hardware Clock from the System Clock, and update the timestamps in
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.IR @ADJTIME_PATH@ .
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With the
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When the
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.B --update-drift
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option (re)calculate the drift factor.
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option is given, then also (re)calculate the drift factor.
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.
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.TP
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.BR \-V , \ \-\-version
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@ -299,7 +298,7 @@ The value of this option is used as an argument to the
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option. For example:
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.RS
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.IP "" 4
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.BI "\%hwclock\ \-\-set\ \-\-date='" 2011-08-14\ 16:45:05 '
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.B "hwclock\ \-\-set\ \-\-date='2011-08-14\ 16:45:05'
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.PP
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The argument must be in local time, even if you keep your Hardware Clock in
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UTC. See the
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@ -382,7 +381,7 @@ as recorded in
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will be used. If the adjtime file doesn't exist, the default is UTC.
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.sp
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Note: daylight saving time changes may be inconsistent when the
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Hardware Clock is kept in local time. See the discussion below under
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Hardware Clock is kept in local time. See the discussion below, under
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.BR "LOCAL vs UTC" .
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.
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.TP
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@ -448,9 +447,9 @@ option to be used. See the discussion below, under
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.TP
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.B \-\-arc
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This option is equivalent to
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.BI \%\-\-epoch= 1980
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.B \%\-\-epoch=1980
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and is used to specify the most common epoch on Alphas
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with ARC console (but Ruffians have an epoch of 1900).
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with an ARC console (although Ruffians have an epoch of 1900).
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.
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.TP
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.BI \-\-epoch= year
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@ -463,7 +462,7 @@ option to set the kernel's idea of the epoch of the Hardware Clock.
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For example, on a Digital Unix machine:
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.RS
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.IP "" 4
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.BI hwclock\ \-\-setepoch\ \-\-epoch= 1952
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.B hwclock\ \-\-setepoch\ \-\-epoch=1952
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.RE
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.
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.TP
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@ -482,15 +481,15 @@ is mounted.
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option is used for Jensen models;
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.B \%\-\-funky\-toy
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means that the machine requires the UF bit instead of the UIP bit in
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the Hardware Clock to detect a time transition. "Toy" in the option
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the Hardware Clock to detect a time transition. The "toy" in the option
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name refers to the Time Of Year facility of the machine.
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.
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.TP
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.B \-\-srm
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This option is equivalent to
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.BI \%\-\-epoch= 1900
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.B \%\-\-epoch=1900
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and is used to specify the most common epoch on Alphas
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with SRM console.
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with an SRM console.
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.
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.SH NOTES
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.
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@ -557,11 +556,11 @@ file, as explained in the man page for
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However, some programs and fringe parts of the Linux kernel such as filesystems
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use the kernel's timezone value. An example is the vfat filesystem. If the
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kernel timezone value is wrong, the vfat filesystem will report and set the
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wrong timestamps on files. Another example is the kernel's NTP \%'11\ minute\ mode.'
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wrong timestamps on files. Another example is the kernel's NTP \%'11\ minute\ mode'.
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If the kernel's timezone value and/or the
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.I \%persistent_clock_is_local
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variable are wrong, then the Hardware Clock will be set incorrectly
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by \%'11\ minute\ mode.' See the discussion below, under
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by \%'11\ minute\ mode'. See the discussion below, under
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.BR "Automatic Hardware Clock Synchronization by the Kernel" .
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.PP
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.B \%hwclock
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@ -589,7 +588,7 @@ compatible system, there is probably no need for users to have the direct
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ISA I/O method, so do not bother. See the
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.BR \-\-rtc " option."
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.PP
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In any case, hwclock will not allow you to set anything unless you have the
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In any case, \fBhwclock\fR will not allow you to set anything unless you have the
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superuser real uid. (This restriction is not necessary if you haven't
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installed setuid root, but it's there for now.)
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.
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@ -782,7 +781,7 @@ Hardware Clock timescale configuration is changed, then a reboot is required to
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notify the kernel.
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.PP
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.B \%hwclock\ \-\-adjust
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should not be used with NTP \%'11\ minute\ mode.'
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should not be used with NTP \%'11\ minute\ mode'.
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.
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.SS ISA Hardware Clock Century value
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.PP
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@ -810,15 +809,15 @@ are supported by the hardware.
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.PP
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This discussion is based on the following conditions:
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.IP \(bu 2
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Nothing is running that alters the date-time clocks, e.g.,
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.BR \%ntpd "(1), cron jobs, et al."
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Nothing is running that alters the date-time clocks, such as
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.BR \%ntpd "(1) or a cron job."
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.IP \(bu 2
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The system timezone is configured for the correct local time. See below
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The system timezone is configured for the correct local time. See below, under
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.BR "POSIX vs 'RIGHT'" .
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.IP \(bu 2
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Early in startup the following are called in this order:
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Early during startup the following are called, in this order:
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.br
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.BI \%adjtimex\ \-\-tick \ <value>\ \-\-frequency \ <value>
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.BI \%adjtimex\ \-\-tick \ value\ \-\-frequency \ value
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.br
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.B \%hwclock\ \-\-hctosys
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.IP \(bu 2
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@ -843,8 +842,7 @@ different for each of them. However, most systems are configured to
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exchange values between these two clocks at startup and shutdown. Now
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the individual device's time keeping errors are transferred back and
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forth between each other. Attempt to configure drift correction for only
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one of them, and the other's drift will be overlaid upon it. If the big
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picture is not kept in mind, confusion will soon ensue.
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one of them, and the other's drift will be overlaid upon it.
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.PP
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This problem can be avoided when configuring drift correction for the
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System Clock by simply not shutting down the machine. This, plus the
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@ -856,11 +854,11 @@ should be done first.
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.PP
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The System Clock drift is corrected with the
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.BR \%adjtimex "(8) command's " \-\-tick " and " \%\-\-frequency
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options. These two work together, tick is the course adjustment and
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frequency is the fine adjustment. (For system that do not have an
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options. These two work together: tick is the coarse adjustment and
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frequency is the fine adjustment. (For systems that do not have an
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.BR \%adjtimex " package,"
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.BI \%ntptime\ \-f\ <ppm>
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may be use instead.)
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.BI \%ntptime\ \-f\ ppm
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may be used instead.)
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.PP
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Some Linux distributions attempt to automatically calculate the System
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Clock drift with
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@ -888,27 +886,27 @@ Once the System Clock is ticking smoothly, move on to the Hardware Clock.
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.PP
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As a rule, cold drift will work best for most use cases. This should be
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true even for 24/7 machines whose normal downtime consists of a reboot.
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In that case the drift factor value makes little difference, but on the
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rare occasion that the machine is shutdown for an extended period then
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In that case the drift factor value makes little difference. But on the
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rare occasion that the machine is shut down for an extended period, then
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cold drift should yield better results.
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.PP
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.B Steps to calculate cold drift:
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.IP 1 2
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.RB "Confirm that " ntpd "(1) will not be launched at startup."
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.RB "Ensure that " ntpd "(1) will not be launched at startup."
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.IP 2 2
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.RI The " System Clock " "time must be correct at shutdown!"
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.IP 3 2
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Shutdown the system.
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Shut down the system.
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.IP 4 2
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Let an extended period pass without changing the Hardware Clock.
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.IP 5 2
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Start the system.
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.IP 6 2
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.RB "Immediately use " hwclock " to set the correct time with the"
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.RB "Immediately use " hwclock " to set the correct time, adding the"
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.BR \%\-\-update\-drift " option."
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.PP
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Note: if step six uses
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.RB \%\-\-systohc ,
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Note: if step 6 uses
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.BR \%\-\-systohc ,
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then the System Clock must be set correctly (step 6a) just before doing so.
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.PP
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.RB "Having " hwclock
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