fix: enable orderly poweroff in hyper-v on Azure

Previously Talos would not shutdown gracefully if hyper-v issued the
'perform_shutdown' call. Said call would execute '/sbin/poweroff' which
did not exist in Talos. We hardlink machined to '/sbin/poweroff' and
make it send a shutdown API call to PID 1 machined.

Fixes #5641

Signed-off-by: Philipp Sauter <philipp.sauter@siderolabs.com>

Dockerfile

@@ -419,6 +419,9 @@ COPY --from=pkg-util-linux-amd64 /lib/libmount.* /rootfs/lib/
 COPY --from=pkg-kmod-amd64 /usr/lib/libkmod.* /rootfs/lib/
 COPY --from=pkg-kernel-amd64 /lib/modules /rootfs/lib/modules
 COPY --from=machined-build-amd64 /machined /rootfs/sbin/init
+# the orderly_poweroff call by the kernel will call '/sbin/poweroff'
+RUN ln /rootfs/sbin/init /rootfs/sbin/poweroff
+RUN chmod +x /rootfs/sbin/poweroff
 # NB: We run the cleanup step before creating extra directories, files, and
 # symlinks to avoid accidentally cleaning them up.
 COPY ./hack/cleanup.sh /toolchain/bin/cleanup.sh
@@ -462,6 +465,9 @@ COPY --from=pkg-util-linux-arm64 /lib/libmount.* /rootfs/lib/
 COPY --from=pkg-kmod-arm64 /usr/lib/libkmod.* /rootfs/lib/
 COPY --from=pkg-kernel-arm64 /lib/modules /rootfs/lib/modules
 COPY --from=machined-build-arm64 /machined /rootfs/sbin/init
+# the orderly_poweroff call by the kernel will call '/sbin/poweroff'
+RUN ln /rootfs/sbin/init /rootfs/sbin/poweroff
+RUN chmod +x /rootfs/sbin/poweroff
 # NB: We run the cleanup step before creating extra directories, files, and
 # symlinks to avoid accidentally cleaning them up.
 COPY ./hack/cleanup.sh /toolchain/bin/cleanup.sh

internal/app/machined/main.go

@@ -30,6 +30,7 @@ import (
 	"github.com/talos-systems/talos/internal/app/machined/pkg/runtime/v1alpha1/bootloader"
 	"github.com/talos-systems/talos/internal/app/machined/pkg/system"
 	"github.com/talos-systems/talos/internal/app/machined/pkg/system/services"
+	"github.com/talos-systems/talos/internal/app/poweroff"
 	"github.com/talos-systems/talos/internal/app/trustd"
 	"github.com/talos-systems/talos/internal/pkg/mount"
 	"github.com/talos-systems/talos/pkg/machinery/api/common"
@@ -302,6 +303,11 @@ func main() {
 	case "/trustd":
 		trustd.Main()
 
+		return
+	// Azure uses the hv_utils kernel module to shutdown the node in hyper-v by calling perform_shutdown which will call orderly_poweroff which will call /sbin/poweroff.
+	case "/sbin/poweroff":
+		poweroff.Main()
+
 		return
 	default:
 	}

internal/app/poweroff/main.go

@@ -0,0 +1,39 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package poweroff
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/metadata"
+
+	"github.com/talos-systems/talos/pkg/grpc/middleware/authz"
+	"github.com/talos-systems/talos/pkg/machinery/client"
+	"github.com/talos-systems/talos/pkg/machinery/constants"
+	"github.com/talos-systems/talos/pkg/machinery/role"
+)
+
+// Main is the entrypoint into /sbin/poweroff.
+func Main() {
+	ctx := context.Background()
+
+	md := metadata.Pairs()
+	authz.SetMetadata(md, role.MakeSet(role.Admin))
+	adminCtx := metadata.NewOutgoingContext(ctx, md)
+
+	client, err := client.New(adminCtx, client.WithUnixSocket(constants.APISocketPath), client.WithGRPCDialOptions(grpc.WithTransportCredentials(insecure.NewCredentials())))
+	if err != nil {
+		log.Fatalf(fmt.Errorf("error while creating machinery client: %w", err).Error())
+	}
+
+	err = client.Shutdown(adminCtx)
+	if err != nil {
+		log.Fatalf(fmt.Errorf("error while sending shutdown command: %w", err).Error())
+	}
+}