Getting started

Randomized system jobs

The role modifies the /etc/crontab configuration file to randomize execution times of hourly, daily, weekly and monthly cron jobs. This is done to avoid huge spikes of job execution every day around 06:25 which is the default execution time defined in the Debian and Ubuntu cron package. The randomization is defined with the following rules:

  • Each type of cron job will have randomized minute at which the jobs will be executed.
  • On each host, the role will choose a specific hour for each of the daily, weekly and monthly jobs. The list of allowed hours is defined in the cron__crontab_hours variable.
  • The weekly cron jobs will be executed on either Saturday or Sunday, chosen randomly. you can specify what days to choose from using the cron__crontab_weekday_days variable.
  • The monthly cron jobs will be executed on a randomized day of the first week of a month. This is controlled by the cron__crontab_day_ranges variable.

The randomization is based on the cron__crontab_seed variable (by default uses the value of the inventory_hostname Ansible fact), as well as some additional pseudo-random strings hashed in the cron__crontab_offset_seeds list. The hashes are stored in the debops.cron Ansible local fact script for idempotency; the script can be removed to regenerate a new set of hashes if the resulting execution times are not the desired ones.

Example inventory

debops.cron is included by default in the common.yml DebOps playbook; you don't need to do anything to have it executed.

If you don’t want to let debops.cron manage the cron jobs, you can do this with the following setting in your inventory:

cron__enabled: False

Example playbook

If you are using this role without DebOps, here's an example Ansible playbook that uses the debops.cron role:


- name: Manage cron jobs
  collections: [ 'debops.debops', 'debops.roles01',
                 'debops.roles02', 'debops.roles03' ]
  hosts: [ 'debops_all_hosts', 'debops_service_cron' ]
  become: True

  environment: '{{ inventory__environment | d({})
                   | combine(inventory__group_environment | d({}))
                   | combine(inventory__host_environment  | d({})) }}'


    - role: cron
      tags: [ 'role::cron', 'skip::cron' ]