Collecting logs is disabled by default in the Datadog Agent, you need to enable it in the datadog.yaml with:
Then add this configuration block to your journald.d/conf.yaml file to start collecting your Logs:
To fill source and service attributes, the Agent collects SYSLOG_IDENTIFIER , _SYSTEMD_UNIT and _COMMand set them to the first non empty value. To take advantage of the integration pipelines, Datadog recommends setting the SyslogIdentifier parameter in the systemd service file directly, or in a systemd service override file. Their location depends on your distribution, but you can find the location of the systemd service file by using the command systemctl show -p FragmentPath <unit_name>.
Note: With Agent 7.17+, if container_mode is set to true, the default behavior changes for logs coming from Docker containers. The source attribute of your logs is automatically set to the corresponding short image name of the container instead of simply docker.