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David Scherfgen
Asked: 2013-03-08 23:44:24 +0800 CST

Checking whether there are any cronjobs currently running

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I'm running a webserver in a VM.

In order to create consistent backups, I have to stop Apache, MySQL and other processes for a short time before doing a snapshot of the VM's harddrive (LVM-based).

However, there might be some cronjobs currently running on the VM that need access to the MySQL database. I don't want to interrupt them.

Therefore, I'm looking for a way to determine whether there are currently any cronjobs running. When it's time for a backup, I will wait until I don't "disturb" any cronjob.

Any ideas how to accomplish this?

backup

2 Answers

  1. What you really need to do is use a locking system because anything that checks for the existence/non-existence of something leaves a window of opportunity for a process to launch and create the inconsistent state you're tryiung to avoid.

    Linux provides the flock command there is an example of using it here.

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  2. Best Answer
    if [ $(ps h --ppid `pidof crond` | wc -l) -eq 0 ]; then 
   /run/your/backup
else 
    echo "There are some still running cron jobs."
fi
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