hostagent: Handle SIGTERM signal for better compatibility with macOS launchd

This commit modifies the hostagent to handle not only the SIGINT (Interrupt) signal, but also the SIGTERM signal. This allows the hostagent to gracefully shut down when it receives a SIGTERM signal, which is a common way to request a process to terminate. This change improves the compatibility with macOS launchd, which uses SIGTERM to stop services.

The following are the steps to set up the Docker instance of Lima to start at login using launchd on macOS:
```bash
# Create the docker instance
limactl start template://docker --vm-type vz --rosetta --network vzNAT --tty=false
# Stop the docker instance
limactl stop docker
# Create the launchd plist
echo '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>io.lima-vm.docker</string>
	<key>ProgramArguments</key>
	<array>
		<string>'"$(which limactl)"'</string>
		<string>hostagent</string>
		<string>--pidfile</string>
		<string>ha.pid</string>
		<string>--socket</string>
		<string>ha.sock</string>
		<string>docker</string>
	</array>
	<key>RunAtLoad</key>
	<true/>
	<key>StandardErrorPath</key>
	<string>ha.stderr.log</string>
	<key>StandardOutPath</key>
	<string>ha.stdout.log</string>
	<key>WorkingDirectory</key>
	<string>'"$(limactl list docker --format '{{.Dir}}')"'</string>
</dict>
</plist>' > ~/Library/LaunchAgents/io.lima-vm.docker.plist
# Load the launchd plist and launchd will start the docker instance
launchctl load ~/Library/LaunchAgents/io.lima-vm.docker.plist
```

Signed-off-by: Norio Nomura <norio.nomura@gmail.com>

Author: norio-nomura

cmd/limactl/hostagent.go

@@ -10,6 +10,7 @@ import (
 	"os/signal"
 	"runtime"
 	"strconv"
+	"syscall"
 
 	"github.com/gorilla/mux"
 	"github.com/lima-vm/lima/pkg/hostagent"
@@ -67,8 +68,8 @@ func hostagentAction(cmd *cobra.Command, args []string) error {
 		defer runtime.UnlockOSThread()
 	}
 
-	sigintCh := make(chan os.Signal, 1)
-	signal.Notify(sigintCh, os.Interrupt)
+	signalCh := make(chan os.Signal, 1)
+	signal.Notify(signalCh, os.Interrupt, syscall.SIGTERM)
 
 	stdout := &syncWriter{w: cmd.OutOrStdout()}
 	stderr := &syncWriter{w: cmd.ErrOrStderr()}
@@ -82,7 +83,7 @@ func hostagentAction(cmd *cobra.Command, args []string) error {
 	if nerdctlArchive != "" {
 		opts = append(opts, hostagent.WithNerdctlArchive(nerdctlArchive))
 	}
-	ha, err := hostagent.New(instName, stdout, sigintCh, opts...)
+	ha, err := hostagent.New(instName, stdout, signalCh, opts...)
 	if err != nil {
 		return err
 	}

pkg/hostagent/hostagent.go

@@ -19,6 +19,7 @@ import (
 	"github.com/lima-vm/lima/pkg/driver"
 	"github.com/lima-vm/lima/pkg/driverutil"
 	"github.com/lima-vm/lima/pkg/networks"
+	"github.com/lima-vm/lima/pkg/osutil"
 
 	"github.com/lima-vm/lima/pkg/cidata"
 	guestagentapi "github.com/lima-vm/lima/pkg/guestagent/api"
@@ -48,7 +49,7 @@ type HostAgent struct {
 	onClose         []func() error // LIFO
 
 	driver   driver.Driver
-	sigintCh chan os.Signal
+	signalCh chan os.Signal
 
 	eventEnc   *json.Encoder
 	eventEncMu sync.Mutex
@@ -79,7 +80,7 @@ func WithNerdctlArchive(s string) Opt {
 // New creates the HostAgent.
 //
 // stdout is for emitting JSON lines of Events.
-func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt) (*HostAgent, error) {
+func New(instName string, stdout io.Writer, signalCh chan os.Signal, opts ...Opt) (*HostAgent, error) {
 	var o options
 	for _, f := range opts {
 		if err := f(&o); err != nil {
@@ -179,7 +180,7 @@ func New(instName string, stdout io.Writer, sigintCh chan os.Signal, opts ...Opt
 		sshConfig:         sshConfig,
 		portForwarder:     newPortForwarder(sshConfig, sshLocalPort, rules, inst.VMType),
 		driver:            limaDriver,
-		sigintCh:          sigintCh,
+		signalCh:          signalCh,
 		eventEnc:          json.NewEncoder(stdout),
 		vSockPort:         vSockPort,
 		virtioPort:        virtioPort,
@@ -418,8 +419,8 @@ func (a *HostAgent) startRoutinesAndWait(ctx context.Context, errCh chan error)
 			}
 			err := a.driver.Stop(ctx)
 			return err
-		case <-a.sigintCh:
-			logrus.Info("Received SIGINT, shutting down the host agent")
+		case sig := <-a.signalCh:
+			logrus.Infof("Received %s, shutting down the host agent", osutil.SignalName(sig))
 			cancelHA()
 			if closeErr := a.close(); closeErr != nil {
 				logrus.WithError(closeErr).Warn("an error during shutting down the host agent")

pkg/osutil/osutil_unix.go

@@ -2,8 +2,17 @@
 
 package osutil
 
-import "golang.org/x/sys/unix"
+import (
+	"os"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
 
 func Ftruncate(fd int, length int64) (err error) {
 	return unix.Ftruncate(fd, length)
 }
+
+func SignalName(sig os.Signal) string {
+	return unix.SignalName(sig.(syscall.Signal))
+}

pkg/osutil/osutil_windows.go

@@ -3,6 +3,7 @@ package osutil
 import (
 	"fmt"
 	"io/fs"
+	"os"
 	"syscall"
 
 	"golang.org/x/sys/windows"
@@ -36,3 +37,14 @@ func SysKill(pid int, _ Signal) error {
 func Ftruncate(_ int, _ int64) (err error) {
 	return fmt.Errorf("unimplemented")
 }
+
+func SignalName(sig os.Signal) string {
+	switch sig {
+	case syscall.SIGINT:
+		return "SIGINT"
+	case syscall.SIGTERM:
+		return "SIGTERM"
+	default:
+		return fmt.Sprintf("Signal(%d)", sig)
+	}
+}