botanist is a tool used by the infrastructure to set up the bot environment before running tests. It handles setting some environment variables used by the other tools it invokes and also handles the initial starting up of the target(s) it will run the tests on.
botanist run is the subcommand which is used by most of the builders run by the infrastructure. It takes a device config and image manifest and starts up the corresponding target in the device config. It also takes a command to run after starting up the targets. Usually this will be testrunner which takes in a test manifest containing the tests to run.
The continuous integration infrastructure sets several flags on botanist to configure it to output logs to a special directory that will be uploaded to cloud storage upon task completion, to be downloaded by the top-level tryjob for presentation to users.
When running against a target that supports SSH, botanist streams syslogs from the target for the duration of the subprocess that it starts.
The syslog is streamed from the target device by running the log_listener command over SSH, and writing it to the local file specified by -syslog.
See: //src/diagnostics/log_listener/README.md
botanist also collects serial logs from devices that support a serial connection, outputting the logs to the local path specified by -serial-log.