How can you run dbt only on modified files?

Running dbt only on modified files can be accomplished by using the command 'dbt run --changed'. This command specifically identifies models that have been modified since the last run and executes them, ensuring that only the altered parts of the data transformation process are re-executed. This feature is valuable for optimizing workflow and resource usage, particularly in large projects where re-running entire dbt jobs can be time-consuming.

In contrast, the other commands serve different purposes: 'dbt run --all' would execute all models in the project without filtering for changes, 'dbt run --incremental' applies to models that are defined as incremental, allowing them to append new data based on specified primary keys, but it does not limit the run to only modified files and is dependent on model configurations. 'dbt run --update' is not a valid dbt command, which further distinguishes 'dbt run --changed' as the most appropriate option for this specific need.