tickadj(8)

NAME

tickadj - set time-related kernel variables

SYNOPSIS

tickadj [ -Aqs ] [ -a tickadj ] [ -t tick ]

DESCRIPTION

The tickadj program reads, and optionally modifies, sever

al 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 /dev/kmem. 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 tickadj include tick, which is the number of

microseconds added to the system time for a clock interrupt,

tickadj, which sets the slew rate and resolution used by the adj

time system call, and dosynctodr, 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.

By default, with no arguments, tickadj reads the variables

of interest in the kernel and displays them. At the same time, it

determines an "optimal" value for the value of the tickadj vari

able if the intent is to run the ntpd Network Time Protocol (NTP)

daemon, and prints this as well. Since the operation of tickadj

when reading the kernel mimics the operation of similar parts of

the ntpd program fairly closely, this can be useful when debug

ging problems with ntpd.

Note that tickadj should be run with some caution when be

ing used for the first time on different types of machines. The

operations which tickadj tries to perform are not guaranteed to

work on all Unix machines and may in rare cases cause the kernel

to crash.

OPTIONS

-a tickadj

Set the kernel variable tickadj to the value tick

adjspecified.

-A Set the kernel variable tickadj to an internally

computed "optimal" value.

-t tick

Set the kernel variable tick to the value tick

specified.

-s Set the kernel variable dosynctodr to zero, which

disables the hardware time-of-year clock, a prerequisite for run

ning the ntpd daemon under SunOS4.

-q Normally, tickadj is quite verbose about what it is

doing. The -q flag tells it to shut up about everything except

errors.

FILES

/vmunix

/unix

/dev/kmem

BUGS

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 adjtime in

many kernels and/or brokenness of the system clock in some ven

dors' kernels. It would be much better if the kernels were fixed

and the tickadj program went away.

Network Time Protocol October 7, 2006

TICKADJ(8)