[linux installer script] Deprecate Fluentd support (#6264)

* [linux installer script] Deprecate Fluentd support

* Update CHANGELOG.md

* Add replacement note to deprecation warnings

Author: crobert-1

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## Unreleased
 
+### 🚩 Deprecations 🚩
+
+- (Splunk) `Linux installer script`: Fluentd support has been deprecated and will be removed in a future release. ([#6264](https://github.com/signalfx/splunk-otel-collector/pull/6264))
+  - Please use native OTel Collector receivers instead.
+  - A common replacement for Fluentd's functionality is the [filelog receiver](https://help.splunk.com/en/splunk-observability-cloud/manage-data/available-data-sources/supported-integrations-in-splunk-observability-cloud/opentelemetry-receivers/filelog-receiver).
+    Many common configuration examples of the `filelog` receiver can be found in the [logs_config_linux.yaml](https://github.com/signalfx/splunk-otel-collector/blob/87bee7ae45b08be8d143a758d0f7004fd92d8f60/cmd/otelcol/config/collector/logs_config_linux.yaml) file.
+
 ## v0.126.0
 
 This Splunk OpenTelemetry Collector release includes changes from the [opentelemetry-collector v0.126.0](https://github.com/open-telemetry/opentelemetry-collector/releases/tag/v0.126.0)

packaging/installer/install.sh

@@ -929,7 +929,7 @@ Collector:
                                         target system that provides the 'splunk-otel-collector' deb/rpm package.
   --test                                Use the test package repo instead of the primary.
 
-Fluentd:
+Fluentd [DEPRECATED]:
   --with[out]-fluentd                   Whether to install and configure fluentd to forward log events to the collector.
                                         (default: --without-fluentd)
   --skip-fluentd-repo                   By default, a apt/yum repo definition file will be created to download the
@@ -1327,6 +1327,7 @@ parse_args_and_install() {
         ;;
       --with-fluentd)
         with_fluentd="true"
+        echo "[WARNING] Fluentd support has been deprecated and will be removed in a future release. Please use native OTel receivers instead (e.g. the filelog receiver)." >&2
         if ! fluentd_supported; then
           echo "[WARNING] Ignoring the --with-fluentd option since fluentd is currently not supported for ${distro}:${distro_version} ${distro_arch}." >&2
         fi