1tickadj(8) System Manager's Manual tickadj(8)
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6 tickadj - set time-related kernel variables
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10 tickadj [ tick ]
11 tickadj [ -Aqs ] [ -a tickadj ] [ -t tick ]
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16 The tickadj program reads, and optionally modifies, several timekeep‐
17 ing-related variables in older kernels that do not have support for
18 precision ttimekeeping, including HP-UX, SunOS, Ultrix, SGI and proba‐
19 bly others. Those machines provide means to patch the kernel /dev/kmem.
20 Newer machines with kernel time support, including Solaris, Tru64,
21 FreeBSD and Linux, should NOT use the program, even if it appears to
22 work, as it will destabilize the kernel time support. Use the ntptime
23 program instead.
24 The particular variables that can be changed with tickadj include tick,
26 which is the number of microseconds added to the system time for a
27 clock interrupt, tickadj, which sets the slew rate and resolution used
28 by the adjtime system call, and dosynctodr, which indicates to the ker‐
29 nels on some machines whether they should internally adjust the system
30 clock to keep it in line with time-of-day clock or not.
31 On Linux, only the tick variable is supported and the only allowed
33 argument is the tick value.
34 By default, with no arguments, tickadj reads the variables of interest
36 in the kernel and displays them. At the same time, it determines an
37 "optimal" value for the value of the tickadj variable if the intent is
38 to run the ntpd Network Time Protocol (NTP) daemon, and prints this as
39 well. Since the operation of tickadj when reading the kernel mimics the
40 operation of similar parts of the ntpd program fairly closely, this can
41 be useful when debugging problems with ntpd.
42 Note that tickadj should be run with some caution when being used for
44 the first time on different types of machines. The operations which
45 tickadj tries to perform are not guaranteed to work on all Unix
46 machines and may in rare cases cause the kernel to crash.
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50 -a tickadj
51 Set the kernel variable tickadj to the value tickadjspecified.
52 -A Set the kernel variable tickadj to an internally computed
54 "optimal" value.
55 -t tick Set the kernel variable tick to the value tick specified.
57 -s Set the kernel variable dosynctodr to zero, which disables the
59 hardware time-of-year clock, a prerequisite for running the
60 ntpd daemon under SunOS 4.x.
61 -q Normally, tickadj is quite verbose about what it is doing. The
63 -q flag tells it to shut up about everything except errors.
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67 /vmunix /unix /dev/kmem
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71 Fiddling with kernel variables at run time as a part of ordinary opera‐
72 tions is a hideous practice which is only necessary to make up for
73 deficiencies in the implementation of adjtime in many kernels and/or
74 brokenness of the system clock in some vendors' kernels. It would be
75 much better if the kernels were fixed and the tickadj program went
76 away.
77
79 ntpd(8)
80 HTML documentation in ntp-doc package.
82 This file was automatically generated from HTML source.
84 tickadj(8)