Understanding Ansible Playbook Failures in Cron Jobs

If your Ansible playbook runs smoothly from the command line but fails when scheduled through a cron job, the culprit is often the difference in environments between interactive sessions and cron jobs. In this post, we'll break down the problem and guide you through a straightforward solution.

The Problem:

1. Environment Variables: When you run commands interactively, your shell environment includes various variables that may not be present when the same command runs from a cron job. This can lead to issues with finding essential executables like ansible-playbook.
2. Working Directory Differences: Cron jobs don't always run from the same directory you expect. If your playbook uses relative paths, it might not find files or resources correctly when executed from a cron job.

Understanding the Issue:

1. Cron Jobs Run in a Limited Environment: Cron jobs run with a minimal set of environment variables. This can impact the ability to locate executables and resources.
2. Path and Working Directory Differences: Commands in cron jobs may not execute from the same directory as your interactive shell. Relative paths in your playbook might break due to these differences.

The Solution:

1. Identify the Full Path to ansible-playbook: Use the which ansible-playbook command to find the full path to the ansible-playbook executable. Use this path explicitly in your cron job entry.
2. Use Absolute Paths in Cron Jobs: Update your cron job entries to use absolute paths for the Ansible executable and playbook files. For example:

15 15 * * * /full/path/to/ansible-playbook -i /path/to/inventory /path/to/playbook.yml --vault-password-file  > /path/to/output.log 2>&1
        

1. Check and Redirect Output: Redirect the output of your cron job to a log file (> /path/to/output.log 2>&1). This helps capture any errors that might occur during playbook execution.

Conclusion:

By addressing environment variables and ensuring the use of absolute paths, you eliminate common pitfalls that cause Ansible playbook failures in cron jobs. These adjustments ensure consistent execution whether running interactively or scheduled via cron.

Happy automating!