Vixie Cron and the new US DST

So, the new DST changes in the US caused a small stir among system administrators recently. We got all of our servers updated and verified they were working before the even. Or so we thought.

I noticed today that our 3PM Eastern newsletters arrived in my inbox at 3PM alright. However, I am in Central time. My immediate assumption was that we missed the server that sends that email out. Logging in I found the time correct on the server. It had received the appropriate updates thanks to portage. So, what happened? I looked at /etc/crontab and all was fine. I then looked at the system log where cron jobs are logged. Oddly, that log line said the job started at 15:00. I knew that was not correct. I started looking around at other cron jobs on other servers, especially ones that wrote files to disk. Sure enough, every server I checked was doing things an hour behind except one. It just so happens we had restarted cron on this server however last week. We had to shut it down to keep it from causing some errors while we updated the server.

So, long story short, we restarted cron on all the servers. That seems to be the only thing needed. These servers have been running (and crond as well) long before even the announcement of the DST change. I guess vixie cron can’t handle time zone rules changing after he starts. For the record, we are using the latest stable version in Gentoo’s Portage.

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2 Responses to Vixie Cron and the new US DST

  1. sapphirecat says:

    If you have mysqld running, the same advice applies: system timezone rules are only read at startup. You may want to check all your long-running, important daemons, not just crond.

  2. Sean Coates says:

    I also ran into the MySQL problem.. I only updated libc _after_ the DST change, though.

    S

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