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