Running the agent from cron

There is an alternative way to operate the agent. We covered starting one long-running puppet agent process that does its work in set intervals and then goes back to sleep. However, it is also possible to have cron launch a discrete agent process in the same interval. This agent will contact the master once, run the received catalog, and then terminate. This has several advantages, as follows:

• The agent operating system saves resources
• The interval is precise and not subject to skew (when running the background agent, deviations result from the time that elapses during the catalog run), and distributed interval skew can lead to thundering herd effects
• Any agent crash or an inadvertent termination is not fatal

Setting Puppet to run the agent from cron is also very easy to do with Puppet! You can use a manifest like the following:

service { 'puppet': enable => false, }
cron { 'puppet-agent-run':
  user    => 'root',
  command => 'puppet agent --no-daemonize --onetime --logdest=syslog',
  minute  => fqdn_rand(60),
  hour    => absent,
}

The fqdn_rand function computes a distinct minute for each of your agents. Setting the hour property to absent means that the job should run every hour.