Table of Contentsclock - manipulate the CMOS clock /sbin/clock [ -u ] -r
/sbin/clock [ -u ] -w
/sbin/clock [ -u ] -s
/sbin/clock [ -u ] -a clock manipulates the CMOS clock in variaous ways, allowing it to be read or written, and allowing synchronization between the CMOS clock and the kernel's version of the system time. - -u
- Indicates that the CMOS clock is set to Universal Time.
- -r
- Read CMOS clock and print the result to stdout.
- -w
- Write the system time into the CMOS clock.
- -s
- Set the system time from the CMOS clock.
- -a
- Set the system time from the CMOS clock, adjusting the time to correct for systematic error, and writting it back into the CMOS clock.
This option uses the file /etc/adjtime to determine how the clock changes. It contains three numbers:
The first number is the correction in seconds per day (for example, if your clock runs 5 seconds fast each day, the first number should read -5.0).
The second number tells when clock was last used, in seconds since 1/1/1970.
The third number is the remaining part of a second that was left over after the last adjustment.
The following instructions are from the source code:
- a)
- create a file /etc/adjtime containing as the first and only line: '0.0 0 0.0'
- b)
- run clock -au or clock -a, depending on whether your CMOS is in Universal or Local Time. This updates the second number.
- c)
- set your system time using the date command.
- d)
- update your CMOS time using clock -wu or clock -w
- e)
- replace the first number in /etc/adjtime by your correction.
- f)
- put the command clock -au or clock -a in your /etc/rc.local, or let cron(8) start it regularly.
/etc/adjtime
/etc/rc.local - V1.0
- Charles Hedrick, hedrick@cs.rutgers.edu, Apr 1992
- V1.1
- Modified for clock adjustments, Rob Hooft, hooft@chem.ruu.nl, Nov 1992
- V1.2
- Patches by Harald Koenig, koenig@nova.tat.physik.uni-tuebingen.de, applied by Rob Hooft, hooft@EMBL-Heidelberg.DE, Oct 1993
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