Host Access

Dagger Functions execute within containers spawned by the Dagger Engine and do not have direct access to the host system. This "sandboxing" serves a few important purposes:

• Reproducibility: Executing in a well-defined and well-controlled container ensures that a Dagger Function to run the same way every time it is invoked. It also guards against creating "hidden dependencies" on ambient properties of the execution environment that could change at any moment.
• Caching: A reproducible containerized environment makes it possible to cache the result of Dagger Function execution, which in turn allows Dagger to automatically speed up function execution.
• Security: Even when running third-party Dagger Functions sourced from a Git repository, those Dagger Functions will not have default access to your host environment (host files, directories, environment variables, etc.). Access to these host resources can only be granted by explicitly passing them as argument values to the Dagger Function.

This section explains important concepts and techniques for you to know when interacting with the host system using Dagger Functions.