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<title>tickadj - set time-related kernel variables</title>
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<h3><tt>tickadj</tt> - set time-related kernel variables</h3>
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<tt>tickadj [ -Aqs ] [ -a <i>tickadj</i> ] [ -t <i>tick</i> ]</tt>
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The <tt>tickadj</tt> program reads, and optionally modifies,
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several timekeeping-related variables in the running kernel in some
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machines, via <tt>/dev/kmem</tt>. The particular variables it is
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concerned with are <tt>tick</tt>, which is the number of
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microseconds added to the system time during a clock interrupt,
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<tt>tickadj</tt>, which sets the slew rate and resolution used by
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the <tt>adjtime</tt> system call, and <tt>dosynctodr</tt>, which
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indicates to the kernels on some machines whether they should
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internally adjust the system clock to keep it in line with
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time-of-day clock or not.
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<p>Note that this program does NOT work in some kernels, in
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particular Solaris 2.6 or later. See the <a href=
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"solaris-dosynctodr.html">report</a>.</p>
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<p>By default, with no arguments, <tt>tickadj</tt> reads the
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variables of interest in the kernel and displays them. At the same
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time, it determines an "optimal" value for the value of the <tt>
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tickadj</tt> variable if the intent is to run the <tt>ntpd</tt>
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Network Time Protocol (NTP) daemon, and prints this as well. Since
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the operation of <tt>tickadj</tt> when reading the kernel mimics
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the operation of similar parts of the <tt>ntpd</tt> program fairly
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closely, this can be useful when debugging problems with <tt>
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<p>Note that <tt>tickadj</tt> should be run with some caution when
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being used for the first time on different types of machines. The
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operations which <tt>tickadj</tt> tries to perform are not
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guaranteed to work on all Unix machines and may in rare cases cause
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the kernel to crash.</p>
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<h4>Command Line Options</h4>
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<dt><tt>-a <i>tickadj</i></tt></dt>
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<dd>Set the kernel variable <tt>tickadj</tt> to the value <i><tt>
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tickadj</tt></i>specified.</dd>
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<dd>Set the kernel variable <tt>tickadj</tt> to an internally
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computed "optimal" value.</dd>
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<dt><tt>-t <i>tick</i></tt></dt>
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<dd>Set the kernel variable <tt>tick</tt> to the value <i><tt>
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tick</tt></i> specified.</dd>
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<dd>Set the kernel variable <tt>dosynctodr</tt> to zero, which
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disables the hardware time-of-year clock, a prerequisite for
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running the <tt>ntpd</tt> daemon under SunOS4.</dd>
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<dd>Normally, <tt>tickadj</tt> is quite verbose about what it is
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doing. The <tt>-q</tt> flag tells it to shut up about everything
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Fiddling with kernel variables at run time as a part of ordinary
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operations is a hideous practice which is only necessary to make up
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for deficiencies in the implementation of <tt>adjtime</tt> in many
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kernels and/or brokenness of the system clock in some vendors'
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kernels. It would be much better if the kernels were fixed and the
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<tt>tickadj</tt> program went away.
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<a href="index.htm"><img align="left" src="pic/home.gif" alt=
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<address><a href="mailto:mills@udel.edu">David L. Mills
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<mills@udel.edu></a></address>
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