After installing the Stackdriver Logging Agent on a Compute Engine virtual machine, what should you do first?

The first step after installing the Stackdriver Logging Agent on a Compute Engine virtual machine is to configure the application log file as a custom source. This action is essential because the logging agent must know which log files to monitor and how to process them. By specifying the application log file as a custom source, you provide the necessary information for the logging agent to collect and forward log entries from that particular file to Stackdriver Logging.

Once the logging agent is set up to recognize the application's log files, it can begin sending logs to Google Cloud, enabling you to view and analyze them through the Cloud Console. Without this configuration, the logging agent would not know where to find the relevant application logs.

While enabling the Error Reporting API, granting the instance access to Cloud APIs, or creating a log export sink are all important tasks for complete log management and monitoring strategies, these steps typically come after ensuring that the logging agent is correctly set to collect the necessary logs from the application.