Document configuring launch-agent via environment variables

Author: christian-stephen

jekyll/_cci2/runner-installation.adoc

@@ -483,7 +483,7 @@ After setup completes, the Launch Agent starts automatically and begins looking
 
 See: xref:runner-on-kubernetes.adoc[Runner on Kubernetes]
 
-== Configuration file reference
+== Configuration reference
 
 A YAML file is used to configure the launch agent, how it communicates with our servers and how it will launch the task agent.
 
@@ -496,27 +496,35 @@ runner:
   name: RUNNER_NAME
 ```
 
+NOTE: The launch agent can also be configured via environment variables by supplying the `--env` flag to the launch agent command.
+
 === runner.name
+`$LAUNCH_AGENT_RUNNER_NAME`
 
 `RUNNER_NAME` is a unique name assigned to this particular running launch agent. CircleCI recommends using the hostname of the machine so that it can be used to identify the agent when viewing statuses and job results in the CircleCI UI.
 
 === api.auth_token
+`$LAUNCH_AGENT_API_AUTH_TOKEN`
 
 This is a token used to identify the launch agent to CircleCI and can be generated by the CircleCI CLI. An existing token may be shared among many installations, but this token only allows a particular `resource_class` to be specified.
 
 === runner.command_prefix
+`$LAUNCH_AGENT_RUNNER_COMMAND_PREFIX`
 
 This prefix enables you to customize how the task agent process is launched. Using a custom script here can allow you to execute arbitrary commands before and after the task runner. You should take care to ensure the supplied arguments are executed, and the correct exit code is returned from the script upon completion.
 
 === runner.working_directory
+`$LAUNCH_AGENT_RUNNER_WORK_DIR`
 
 This directory allows you to control the default working directory used by each job. If the directory already exists, task agent will need permissions to write to the directory. If the directory does not exist, then the task agent will need permissions to create the directory. If `%s` is present in the value, this value will be replaced with a different value for each job. Note that these directories will not be automatically removed.
 
 === runner.cleanup_working_directory
+`$LAUNCH_AGENT_RUNNER_CLEANUP_WORK_DIR`
 
 This directory enables you to control the working directory cleanup after each job. The default value is `false`.
 
 === runner.mode
+`$LAUNCH_AGENT_RUNNER_MODE`
 
 This parameter allows you to specify whether you want to terminate this runner instance upon completion of a job (single-task) or to continuously poll for new available jobs.
 
@@ -528,6 +536,7 @@ The possible values are:
 NOTE: The default value is continuous.
 
 === runner.max_run_time
+`$LAUNCH_AGENT_RUNNER_MAX_RUN_TIME`
 
 This value can be used to override the default maximum duration the task agent will run each job. Note that the value is a string with the following unit identifiers `h`, `m` or `s` for hour minute and seconds respectively:
 
@@ -553,12 +562,14 @@ Draining can end in one of two ways:
 * An additional TERM signal is received by the Launch Agent during "draining".
 
 === runner.idle_timeout
+`$LAUNCH_AGENT_RUNNER_IDLE_TIMEOUT`
 
 This timeout will enable a launch agent to terminate if no task has been claimed within the given time period. The value is a string with the following unit identifiers: `h`, `m` or `s` for hours, minutes and seconds, respectively (e.g., `5m` is 5 minutes).
 
 NOTE: The default behaviour is to never time out due to inactivity.
 
 === runner.ssh.advertise_addr
+`$LAUNCH_AGENT_RUNNER_SSH_ADVERTISE_ADDR`
 
 This parameter enables the 'Rerun job with SSH' feature. Before enabling this feature, there are xref:runner-installation.adoc#considerations-before-enabling-ssh-debugging[*important considerations that should be made*].