Restart Beat after install on deb package (#36201)

This commit restarts the Beat after the deb package is installed. When
upgrading a Beat via deb packages this is required for the new version
to start running.

The post install script checks whether the Beat is running, if so, then
it restarts the service.

CHANGELOG.next.asciidoc

@@ -61,6 +61,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Eliminate cloning of event in deepUpdate {pull}35945[35945]
 - Fix ndjson parser to store JSON fields correctly under `target` {issue}29395[29395]
 - Support build of projects outside of beats directory {pull}36126[36126]
+- After upgrade the deb package now restarts the Beat service {issue}34089[34089] {pull}36201[36201]
 
 
 

dev-tools/packaging/packages.yml

@@ -19,7 +19,7 @@ shared:
   # Deb/RPM spec for community beats.
   - &deb_rpm_spec
     <<: *common
-    post_install_script: '{{ elastic_beats_dir }}/dev-tools/packaging/files/linux/systemd-daemon-reload.sh'
+    post_install_script: '{{ elastic_beats_dir }}/dev-tools/packaging/templates/deb/postinstall.sh.tmpl'
     files:
       /usr/share/{{.BeatName}}/bin/{{.BeatName}}{{.BinaryExt}}:
         source: build/golang-crossbuild/{{.BeatName}}-{{.GOOS}}-{{.Platform.Arch}}{{.BinaryExt}}
@@ -618,4 +618,4 @@ specs:
           '{{.BeatName}}{{.BinaryExt}}':
             source: data/{{.BeatName}}-{{ commit_short }}/{{.BeatName}}{{.BinaryExt}}
             symlink: true
-            mode: 0755
+            mode: 0755

dev-tools/packaging/templates/deb/postinstall.sh.tmpl

@@ -0,0 +1,6 @@
+#!/usr/bin/sh
+
+systemctl daemon-reload 2> /dev/null
+systemctl is-active {{.BeatName}} --quiet && systemctl restart {{.BeatName}}
+exit 0
+