On my CentOS 5.6, when I do 'service anacron status', I get some 'anacron is stopped', but on my CentOS 6.0, when I do 'service anacron status' it says there's no service called anacron. But for both systems if I do 'which anacron' I get /usr/sbin/anacron.

So I'm wondering on the system where there is no anacron service, how does it run? (Because it does seem to be running the daily run.) There doesn't seem to be any anacron script in /etc/cron.daily/ or /etc/cron.d/, and /etc/crontab doesn't have any entries.

I tried to search through the processes doing a 'ps aux | grep anacron' on both systems, and nothing appeared.

So how does it run on a daily basis as it's supposed to?

So anacron is part of the cronie-anacron. Looking further provides the answer to your question: