dist/ntp/html/tickadj.html

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  13                 <h3><tt>tickadj</tt> - set time-related kernel variables</h3>
  14                 <p>Last update: <csobj format="ShortTime" h="25" locale="00000409" region="0" t="DateTime" w="61">18:50</csobj> UTC <csobj format="LongDate" h="25" locale="00000409" region="0" t="DateTime" w="246">Thursday, July 28, 2005</csobj></p>
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  16                 <h4>Synopsis</h4>
  17                 <tt>tickadj [ -Aqs ] [ -a <i>tickadj</i> ] [ -t <i>tick</i> ]</tt>
  18                 <h4>Description</h4>
  19                 <p>The <tt>tickadj</tt> program reads, and optionally modifies, several timekeeping-related variables in older kernels that do not have support for precision ttimekeeping, including HP-UX, SunOS, Ultrix, SGI and probably others. Those machines provide means to patch the kernel <tt>/dev/kmem</tt>. Newer machines with precision time support, including Solaris, Tru64, FreeBSD and Linux (with PPSkit patch) should NOT use the program. The particular variables that can be changed with <tt>tickadj</tt> include <tt>tick</tt>, which is the number of microseconds added to the system time for a clock interrupt, <tt>tickadj</tt>, which sets the slew rate and resolution used by the <tt>adjtime</tt> system call, and <tt>dosynctodr</tt>, which indicates to the kernels on some machines whether they should internally adjust the system clock to keep it in line with time-of-day clock or not.</p>
  20                 <p>By default, with no arguments, <tt>tickadj</tt> reads the variables of interest in the kernel and displays them. At the same time, it determines an &quot;optimal&quot; value for the value of the <tt>tickadj</tt> variable if the intent is to run the <tt>ntpd</tt> Network Time Protocol (NTP) daemon, and prints this as well. Since the operation of <tt>tickadj</tt> when reading the kernel mimics the operation of similar parts of the <tt>ntpd</tt> program fairly closely, this can be useful when debugging problems with <tt>ntpd</tt>.</p>
  21                 <p>Note that <tt>tickadj</tt> should be run with some caution when being used for the first time on different types of machines. The operations which <tt>tickadj</tt> tries to perform are not guaranteed to work on all Unix machines and may in rare cases cause the kernel to crash.</p>
  22                 <h4>Command Line Options</h4>
  23                 <dl>
  24                         <dt><tt>-a <i>tickadj</i></tt>
  25                         <dd>Set the kernel variable <tt>tickadj</tt> to the value <i><tt>tickadj</tt></i>specified.
  26                         <dt><tt>-A</tt>
  27                         <dd>Set the kernel variable <tt>tickadj</tt> to an internally computed &quot;optimal&quot; value.
  28                         <dt><tt>-t <i>tick</i></tt>
  29                         <dd>Set the kernel variable <tt>tick</tt> to the value <i><tt>tick</tt></i> specified.
  30                         <dt><tt>-s</tt>
  31                         <dd>Set the kernel variable <tt>dosynctodr</tt> to zero, which disables the hardware time-of-year clock, a prerequisite for running the <tt>ntpd</tt> daemon under SunOS4.
  32                         <dt><tt>-q</tt>
  33                         <dd>Normally, <tt>tickadj</tt> is quite verbose about what it is doing. The <tt>-q</tt> flag tells it to shut up about everything except errors.
  34                 </dl>
  35                 <h4>Files</h4>
  36                 <pre>
  37 /vmunix
  38
  39 /unix
  40
  41 /dev/kmem
  42 </pre>
  43                 <h4>Bugs</h4>
  44                 Fiddling with kernel variables at run time as a part of ordinary operations is a hideous practice which is only necessary to make up for deficiencies in the implementation of <tt>adjtime</tt> in many kernels and/or brokenness of the system clock in some vendors' kernels. It would be much better if the kernels were fixed and the <tt>tickadj</tt> program went away.
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