Run cron in background, but "/sbin/chkconfig: command not found"

I’m trying to set up a cron, and wanted to see first how this works whole. I followed this tutorial:

https://www.digitalocean.com/community/articles/how-to-use-cron-to-automate-tasks-on-a-vps

There is also in it, that you should tell the cron he should run in the background:

You’ll need to make sure it runs in the background too:

sudo / sbin / chkconfig crond on sudo / sbin / service crond start

But as soon as I type one of these commands, I get the message "/ sbin / service: command not found …