[8.x](backport #4615) Add the OTel quickstart (#4758)

Author: mergify[bot]

docs/en/observability/images/quickstart-monitor-hosts-otel-entry-point.png

@@ -22,6 +22,8 @@ include::quickstarts/monitor-hosts-with-elastic-agent.asciidoc[leveloffset=+2]
 
 include::quickstarts/monitor-k8s-logs-metrics.asciidoc[leveloffset=+2]
 
+include::quickstarts/monitor-hosts-with-otel.asciidoc[leveloffset=+2]
+
 include::quickstarts/monitor-k8s-otel.asciidoc[leveloffset=+2]
 
 include::quickstarts/collect-data-with-aws-firehose.asciidoc[leveloffset=+2]

docs/en/observability/index.asciidoc

@@ -0,0 +1,70 @@
+[[quickstart-monitor-hosts-with-otel]]
+= Quickstart: Monitor hosts with OpenTelemetry
+
+preview::[]
+
+In this quickstart guide, you'll learn how to monitor your hosts using the Elastic Distribution of OpenTelemetry (EDOT) Collector.
+You'll also learn how to use {observability} features to gain deeper insight into your observability data after collecting it.
+
+[discrete]
+== Prerequisites
+
+* An {es} cluster for storing and searching your data, and {kib} for visualizing and managing your data. This quickstart is available for all Elastic deployment models. The quickest way to get started with this quickstart is using a trial project on {serverless-docs}/quickstart-monitor-hosts-with-otel.html[Elastic serverless].
+* This quickstart is only available for Linux and MacOS systems.
+* A user with the **Admin** role or higher—required to onboard system logs and metrics. To learn more, refer to {cloud}/ec-user-privileges.html[User roles and privileges].
+* Root privileges on the host—required to run the OpenTelemetry collector because of these components:
+** `hostmetrics` receiver to read all system metrics (all processes, memory, etc.).
+** `filelog` to allow the collector to read any user or application log files.
+
+
+[discrete]
+== Limitations
+Refer to https://github.com/elastic/opentelemetry/blob/main/docs/collector-limitations.md[Elastic OpenTelemetry Collector limitations] for known limitations when using the EDOT Collector.
+
+[discrete]
+== Collect your data
+
+Follow these steps to collect logs and metrics using the EDOT Collector:
+
+. In {kib}, go to the **Observability** UI and click **Add Data**.
+. Under **What do you want to monitor?** select **Host**, and then select **OpenTelemetry: Logs & Metrics**.
++
+[role="screenshot"]
+image::images/quickstart-monitor-hosts-otel-entry-point.png[Host monitoring entry point]
+. Select the appropriate platform.
+. Copy the command under step 1, open a terminal on your host, and run the command.
++
+This command downloads the {agent} package, extracts it in a EDOT directory. For example, `elastic-distro-8.16.0-linux-x86_64`.
+It also adds a sample `otel.yml` configuration file to the directory and updates the storage directory, Elastic endpoint, and API key in the file.
++
+The default log path is `/var/log/*.log`. To update the path, modify the `otel.yml` in the EDOT directory.
++
+Find additional sample `otel.yml` configuration files in the EDOT directory in the `otel_samples` folder.
+. Copy the command under Step 2 and run it in your terminal to start the EDOT Collector.
+
+NOTE: Logs are collected from setup onward, so you won't see logs that occurred before starting the EDOT Collector.
+
+Under **Visualize your data**, you'll see links to **Logs Explorer** to view your logs and **Hosts** to view your host metrics.
+
+[discrete]
+== Gain deeper insight into your host data
+
+After using the Hosts page and Discover to confirm you've ingested all the host logs and metrics you want to monitor,
+use Elastic {observability} to gain deeper insight into your host data with the following capabilities and features:
+
+* In the <<monitor-infrastructure-and-hosts,Infrastructure UI>>, analyze and compare data collected from your hosts.
+You can also:
+** <<inspect-metric-anomalies,Detect anomalies>> for memory usage and network traffic on hosts.
+** <<create-alerts,Create alerts>> that notify you when an anomaly is detected or a metric exceeds a given value.
+* In the <<explore-logs,Logs Explorer>>, search and filter your log data,
+get information about the structure of log fields, and display your findings in a visualization.
+You can also:
+** <<monitor-datasets,Monitor log data set quality>> to find degraded documents.
+** {kibana-ref}/xpack-ml-aiops.html#log-pattern-analysis[Run a pattern analysis] to find patterns in unstructured log messages.
+** <<create-alerts,Create alerts>> that notify you when an Observability data type reaches or exceeds a given value.
+* Use {kibana-ref}/xpack-ml.html[machine learning] to apply predictive analytics to your data:
+** {kibana-ref}/xpack-ml-anomalies.html[Detect anomalies] by comparing real-time and historical data from different sources to look for unusual, problematic patterns.
+** {kibana-ref}/xpack-ml-aiops.html#log-rate-analysis[Analyze log spikes and drops].
+** {kibana-ref}/xpack-ml-aiops.html#change-point-detection[Detect change points] in your time series data.
+
+Refer to the <<observability-introduction>> for a description of other useful features.