Merge pull request #65554 from rdodev/kubelet-postinstall-step

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

bazel: kubelet deb package postinstall step

**What this PR does / why we need it**:
Presently bazel build .deb (kubelet.deb specifically) does not auto-restart after installation. Adding a postinst control file fixes this.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
kubernetes/kubeadm#944
**Special notes for your reviewer**:

@chuckha  

```release-note
bazel deb package bugfix: The kubeadm deb package now reloads the kubelet after installation
```

build/debs/BUILD

@@ -164,6 +164,7 @@ k8s_deb(
     description = """Kubernetes Cluster Bootstrapping Tool
 The Kubernetes command line tool for bootstrapping a Kubernetes cluster.
 """,
+    postinst = "postinst",
     version_file = "//build:os_package_version",
 )
 

build/debs/postinst

@@ -0,0 +1,30 @@
+#!/bin/sh
+# see: dh_installdeb(1)
+
+set -o errexit
+set -o nounset
+
+case "$1" in
+    configure)
+        # because kubeadm package adds kubelet drop-ins, we must daemon-reload
+        # and restart kubelet now. restarting kubelet is ok because kubelet
+        # postinst configure step auto-starts it.
+        systemctl daemon-reload 2>/dev/null || true
+        systemctl restart kubelet 2>/dev/null || true
+    ;;
+
+    abort-upgrade|abort-remove|abort-deconfigure)
+    ;;
+
+    *)
+        echo "postinst called with unknown argument \`$1'" >&2
+        exit 1
+    ;;
+esac
+
+# dh_installdeb will replace this with shell code automatically
+# generated by other debhelper scripts.
+
+#DEBHELPER#
+
+exit 0