%% Last Updated: - [[2021-02-09]] %% ## [[Environment variables]] [Injected environment variables](https://k6.io/docs/cloud/creating-and-running-a-test/cloud-tests-from-the-cli#injected-environment-variables-on-the-cloud-execution) are used in k6 to expose certain characteristics regarding the test execution. Sometimes, these are printed to the log upon encountering an error to make troubleshooting easier later. Other times, they are used to generate or consume [[Unique data generation during runtime|unique test data]] `LI_LOAD_ZONE`, `LI_INSTANCE_ID`, `LI_DISTRIBUTION`, ## Execution context variables [Execution context variables](https://k6.io/docs/using-k6/execution-context-variables) or [[Execution Parameters]] are options for further customizing a test script. They can be set at runtime as flags from the CLI. `${__VU}`, `${__ITER}` `k6 run --vus 10 --iterations 100 script.js`