docs: user guides

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

docs/guides/opentelemetry.md

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+# OpenTelemetry support
+
+To capture the trace to [Jaeger](https://github.com/jaegertracing/jaeger), set
+`JAEGER_TRACE` environment variable to the collection address using a `driver-opt`.
+
+First create a Jaeger container:
+
+```console
+$ docker run -d --name jaeger -p "6831:6831/udp" -p "16686:16686" jaegertracing/all-in-one
+```
+
+Then [create a `docker-container` builder](../reference/buildx_create.md)
+that will use the Jaeger instance via the `JAEGER_TRACE` env var:
+
+```console
+$ docker buildx create --use \
+  --name mybuilder \
+  --driver docker-container \
+  --driver-opt "network=host" \
+  --driver-opt "env.JAEGER_TRACE=localhost:6831"
+```
+
+Boot and [inspect `mybuilder`](../reference/buildx_inspect.md):
+
+```console
+$ docker buildx inspect --bootstrap
+```
+
+Buildx commands should be traced at `http://127.0.0.1:16686/`:
+
+![](https://user-images.githubusercontent.com/1951866/124468052-ef085400-dd98-11eb-84ab-7ac8e261dd52.png)