Linux – How to configure cron to run jobs using specific timezone times

cronlinuxredhat

We have a system configured in local UK time – so its currently in BST and will be switching to GMT this coming weekend.

There are some reports scheduled with cron that are for users in Hong Kong. As they have no Daylight Savings Time, their clocks are not changing.

So – the plan is, as per usual, to adjust the times of their reports back an hour.

Is there a way to tell cron to run at a specific timezone time, for example run job1 at 9am localtime, run job2 at 10am HK time?

I see from this question that you can specify a timezone in the crontab file, but that seems to affect the timezone of the environment under which commands are run and not the time at which the jobs are run.

Thanks in advance for any tips.
Chris

Best Answer

Sure, you can. Try this:

0 9 * * * job1
TZ=Asia/Hong_Kong
0 10 * * * job2

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There are a couple of programs that automate this feature, take away the annoyance and potential bugs from doing this yourself, and avoid the stale lock problem by using flock behind the scenes, too (which is a risk if you're just using touch). I've used lockrun and lckdo in the past, but now there's flock(1) (in newish versions of util-linux) which is great. It's really easy to use:

* * * * * /usr/bin/flock -n /tmp/fcj.lockfile /usr/local/bin/frequent_cron_job

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I think you're trying to have it both ways and the reality is that you just can't. If you want a job to run at 8 AM local time, for example, regardless of whether daylight saving is active then you either run your system (and cron) in local time and don't do seasonal edits or you run it in UTC (not GMT) and do seasonal edits. If you want your jobs to run at the same UTC, regardless, then you run cron according to UTC and there's nothing more to do.

If what you want is for a user to be able to schedule a cron job according to his local time zone and not have him have to think about conversions for his convenience then you write a conversion script that accepts a cron spec and a time zone then does the conversion to UTC behind the scenes and edits the crontab for him. It could even be a two-way conversion to handle changes to existing entries.

It will be helpful if you tell us what you're actually trying to accomplish.

Best Answer

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