[SOLVED] What are the risks involved in restarting crond?

gabriot · 06-25-2012, 10:06 AM

Basically I'm seeing that crond has some very long running processes that are taking up CPU on a total of 4 servers. I restarted crond on the server that had what looked to be the least important "stuff" in the crontab, and it completely fixed the CPU issue. However, before I restart crond on the other servers, I just want to make sure that I am not potentially borking the system by doing so... I assume whatever operations that crond are set to perform in the crontab will resume when I restart it correct?

MensaWater · 06-25-2012, 10:26 AM

crond is a scheduler. If you stop it and it isn't currently in the middle of a process it hurts nothing. When you restart it then it runs things as scheduled as it doesn't care which invocation you did.

Note however that "at" jobs (vs. "cron" jobs) are submitted on the fly but controlled by crond - if you have any "at" jobs you might need to verity they're still there after the restart with "at -l" and if not resubmit them.

gabriot · 06-25-2012, 10:33 AM

Thanks for the quick response!

So apologies for my noob-ness, but if I run "at -l" and it says command not found, is it safe to assume i don't have any "at" jobs?

unSpawn · 06-25-2012, 10:49 AM

Quote:

Originally Posted by MensaWater

at" jobs (vs. "cron" jobs) are submitted on the fly but controlled by crond

At jobs are run and controlled by the at daemon.

Quote:

Originally Posted by gabriot

is it safe to assume i don't have any "at" jobs?

Don't assume but run 'atq' to see if you have any at jobs or look in /var/spool/at.

unSpawn · 06-25-2012, 10:55 AM

*BTW the problem with your previous thread (http://www.linuxquestions.org/questi...ly-4175412544/) is that the cause for resource hogging was never identified. In this thread you speak about "very long running processes" but without being specific. In some cases you might be able to assign a task to a specific CPU, nice the job or ionice it but it depends. Some jobs just require much resources.

MensaWater · 06-25-2012, 11:30 AM

Quote:

Originally Posted by unSpawn

At jobs are run and controlled by the at daemon.

Not on all *NIX systems.

gabriot · 06-25-2012, 05:56 PM

Thanks for the information everyone! I had to "do it live" bill o'reilly style and went ahead and restarted crond, and it looks to be ok. It resolved the CPU on all the servers except one, I'm going to have to start a separate thread since it looks to be a different issue that is also over my head.

unSpawn · 06-25-2012, 06:55 PM

Quote:

Originally Posted by MensaWater

Not on all *NIX systems.

It would be interested to know which Linux distributions (not other Operating Systems, after all this question was asked in the Linux Newbie forum) still use a cron job atrun entry (which basically runs atd anyway) and not for backward compatibility reasons?