On my Ubuntu 11.04 server when I try to run
service powernap stop
as a cron job with the root user, it fails and gives me this message in syslog
NAS CRON: (CRON) error (grandchild #10854 failed with exit status 2)
and this is emailed to the root users email account
exec: 129: stop: not found
I can start and stop the powernap service from the command line so why doesn't it work from cron?