change system time via crontab?

[Mike_Ca Li]

change date of a HPUX 11i server via crontab:

I have a shell script which I want to run by crontab :
like
start:
#!/usr/bin/sh
date 07311600
end
to change date of server to July 31 2004 and I set job to run at
00 16 * * 2 /usr/local/bin/timescript
However the system time does not change.
Why would that be?

[Steven E. Protter]

You can do anything witha s script. I don't think its a good practice to change system time with a cron script triggered by system time.

You can inadvertantly cause a loop.

Best that be done manually or via ntp(network time protocol).

SEP

[Mike_Ca Li]

I need to change the date and not the time.
wouldn't running

00 17 * * 2 /usr/local/bin/changetimescript

changetimescript:
date 07311700

provide a more accurate time change than doing typing command
date 07311700 at 16:59:50 from keyboard?

[Michael Tully]

Why not set up NTP to bounce of your router. It will take less than 5 minutes to set up.

If you have databases on your system, they don't take too kindly to have the time changed, forwards or backwards.

[Muthukumar_5 · Accepted solution]

hai,

cron will be working based on time and date informations. If we change the time and date with a script, in a cronjob, it will make effects on other jobs and crontab too.

I have checked the accuracy of date change on command line as,

# time date 073117342004
unable to write utmps record to wtmps database
unable to write utmps record to wtmps database
Sat Jul 31 17:34:00 PDT 2004

real 0.0
user 0.0
sys 0.0

It cannot write time into logs. But the amount of time needed to change the date and time is in 1 second (average) period only. So you can very well proceed on shell with super privillaged user.

[Thomas Bianco]

seriously consider NTP. it's automatic, simple to configure and avoids that nasty tendancy of database to melt down when somewhat changes the system time.

http://www.ntp.org

all you should have to do is create a /etc/ntp.conf with a single line similar to the following

Server SourceNTP.Server.net

where sourcentp.server.net is the ip or DNS name of a NTP provider, probably within your company.

then start the deamon (/usr/local/bin/ntpd if i am not mistaken) and let it adjust the time.

as for accuracy, i have close to 400 NTP clients in this building, and none of them are more then 10 ms off from the atomic time.