If you're using rbenv, you need to set a custom job type so whenever will hit the rbenv shims. The default job types, such as rake don't.

For example:

job_type :rbenv_rake, %Q{export PATH=/opt/rbenv/shims:/opt/rbenv/bin:/usr/bin:$PATH; eval "$(rbenv init -)"; \
                     cd :path && bundle exec rake :task --silent :output }

Other useful tidbits:

set :environment, :development #useful for testing in development
set :output, 'tmp/whenever.log' #logging

various formats:

#every so often
every 2.minutes do 
  rbenv_rake "jobs:add_listings"
end


#at a certain time every week
every :friday, at: '4:40am' do
  rbenv_rake "jobs:add_listings"
end

To write the crontab from your schedule.rb file:

whenever -w

To view your crontab:

crontab -l

To delete your crontab

whenever -c