Allow passing guestagent location to instance.StartWithPath

This is similar to passing in the full path to limactl to allow an embedding
application stored in a different location to launch a VM.

Simplified the internal calls by removing the limactl argument to instance.Start.

Also changed the order to look for external drivers first in LIMA_DRIVERS_PATH
before looking in libexec, allowing the user to override the drivers in the default
location. This also makes sure that the LIMA_DRIVERS_PATH drivers are found even
when libexec cannot be located.

Signed-off-by: Jan Dubois <jan.dubois@suse.com>

Author: jandubois

cmd/limactl/clone.go

@@ -113,7 +113,7 @@ func cloneAction(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return err
 	}
-	return instance.Start(ctx, newInst, "", false, false)
+	return instance.Start(ctx, newInst, false, false)
 }
 
 func cloneBashComplete(cmd *cobra.Command, _ []string, _ string) ([]string, cobra.ShellCompDirective) {

cmd/limactl/edit.go

@@ -166,7 +166,7 @@ func editAction(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return err
 	}
-	return instance.Start(ctx, inst, "", false, false)
+	return instance.Start(ctx, inst, false, false)
 }
 
 func askWhetherToStart() (bool, error) {

cmd/limactl/shell.go

@@ -106,7 +106,7 @@ func shellAction(cmd *cobra.Command, args []string) error {
 			return err
 		}
 
-		err = instance.Start(ctx, inst, "", false, false)
+		err = instance.Start(ctx, inst, false, false)
 		if err != nil {
 			return err
 		}

cmd/limactl/start.go

@@ -548,7 +548,7 @@ func createAction(cmd *cobra.Command, args []string) error {
 	if len(inst.Errors) > 0 {
 		return fmt.Errorf("errors inspecting instance: %+v", inst.Errors)
 	}
-	if _, err = instance.Prepare(cmd.Context(), inst); err != nil {
+	if _, err = instance.Prepare(cmd.Context(), inst, ""); err != nil {
 		return err
 	}
 	logrus.Infof("Run `limactl start %s` to start the instance.", inst.Name)
@@ -606,7 +606,7 @@ func startAction(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	return instance.Start(ctx, inst, "", launchHostAgentForeground, progress)
+	return instance.Start(ctx, inst, launchHostAgentForeground, progress)
 }
 
 func createBashComplete(cmd *cobra.Command, _ []string, toComplete string) ([]string, cobra.ShellCompDirective) {

pkg/instance/restart.go

@@ -25,7 +25,7 @@ func Restart(ctx context.Context, inst *limatype.Instance, showProgress bool) er
 		return err
 	}
 
-	if err := Start(ctx, inst, "", launchHostAgentForeground, showProgress); err != nil {
+	if err := Start(ctx, inst, launchHostAgentForeground, showProgress); err != nil {
 		return err
 	}
 
@@ -40,7 +40,7 @@ func RestartForcibly(ctx context.Context, inst *limatype.Instance, showProgress
 		return err
 	}
 
-	if err := Start(ctx, inst, "", launchHostAgentForeground, showProgress); err != nil {
+	if err := Start(ctx, inst, launchHostAgentForeground, showProgress); err != nil {
 		return err
 	}
 

pkg/instance/start.go

@@ -44,9 +44,8 @@ type Prepared struct {
 }
 
 // Prepare ensures the disk, the nerdctl archive, etc.
-func Prepare(ctx context.Context, inst *limatype.Instance) (*Prepared, error) {
-	var guestAgent string
-	if !*inst.Config.Plain {
+func Prepare(ctx context.Context, inst *limatype.Instance, guestAgent string) (*Prepared, error) {
+	if !*inst.Config.Plain && guestAgent == "" {
 		var err error
 		guestAgent, err = usrlocalsharelima.GuestAgentBinary(*inst.Config.OS, *inst.Config.Arch)
 		if err != nil {
@@ -131,20 +130,24 @@ func Prepare(ctx context.Context, inst *limatype.Instance) (*Prepared, error) {
 	}, nil
 }
 
-// Start starts the hostagent in the background, which in turn will start the instance.
-// Start will listen to hostagent events and log them to STDOUT until either the instance
+// StartWithPaths starts the hostagent in the background, which in turn will start the instance.
+// StartWithPaths will listen to hostagent events and log them to STDOUT until either the instance
 // is running, or has failed to start.
 //
-// The `limactl` argument allows the caller to specify the full path of the `limactl` executable.
-// When called from inside limactl itself it will always be the empty string which uses the name
-// of the current executable instead.
-//
-// The `launchHostAgentForeground` argument makes the hostagent run in the foreground.
+// The launchHostAgentForeground argument makes the hostagent run in the foreground.
 // The function will continue to listen and log hostagent events until the instance is
 // shut down again.
 //
-// Start calls Prepare by itself, so you do not need to call Prepare manually before calling Start.
-func Start(ctx context.Context, inst *limatype.Instance, limactl string, launchHostAgentForeground, showProgress bool) error {
+// The showProgress argument tells the hostagent to show provision script progress by tailing cloud-init logs.
+//
+// The limactl argument allows the caller to specify the full path of the limactl executable.
+// The guestAgent argument allows the caller to specify the full path of the guest agent executable.
+// Inside limactl this function is only called by Start, which passes empty strings for both
+// limactl and guestAgent, in which case the location of the current executable is used for
+// limactl and the guest agent is located from the corresponding <prefix>/share/lima directory.
+//
+// StartWithPaths calls Prepare by itself, so you do not need to call Prepare manually before calling Start.
+func StartWithPaths(ctx context.Context, inst *limatype.Instance, launchHostAgentForeground, showProgress bool, limactl, guestAgent string) error {
 	haPIDPath := filepath.Join(inst.Dir, filenames.HostAgentPID)
 	if _, err := os.Stat(haPIDPath); !errors.Is(err, os.ErrNotExist) {
 		return fmt.Errorf("instance %q seems running (hint: remove %q if the instance is not actually running)", inst.Name, haPIDPath)
@@ -153,7 +156,7 @@ func Start(ctx context.Context, inst *limatype.Instance, limactl string, launchH
 
 	haSockPath := filepath.Join(inst.Dir, filenames.HostAgentSock)
 
-	prepared, err := Prepare(ctx, inst)
+	prepared, err := Prepare(ctx, inst, guestAgent)
 	if err != nil {
 		return err
 	}
@@ -251,6 +254,10 @@ func Start(ctx context.Context, inst *limatype.Instance, limactl string, launchH
 	}
 }
 
+func Start(ctx context.Context, inst *limatype.Instance, launchHostAgentForeground, showProgress bool) error {
+	return StartWithPaths(ctx, inst, launchHostAgentForeground, showProgress, "", "")
+}
+
 func waitHostAgentStart(_ context.Context, haPIDPath, haStderrPath string) error {
 	begin := time.Now()
 	deadlineDuration := 5 * time.Second

pkg/registry/registry.go

@@ -70,12 +70,11 @@ func CheckInternalOrExternal(name string) string {
 }
 
 func Get(name string) (*ExternalDriver, driver.Driver, bool) {
-	if err := discoverDrivers(); err != nil {
-		logrus.Warnf("Error discovering drivers: %v", err)
-	}
-
 	internalDriver, exists := internalDrivers[name]
 	if !exists {
+		if err := discoverDrivers(); err != nil {
+			logrus.Warnf("Error discovering drivers: %v", err)
+		}
 		externalDriver, exists := ExternalDrivers[name]
 		if exists {
 			return externalDriver, nil, exists
@@ -102,18 +101,6 @@ func registerExternalDriver(name, path string) {
 }
 
 func discoverDrivers() error {
-	stdDriverDir, err := usrlocalsharelima.LibexecLima()
-	if err != nil {
-		return err
-	}
-
-	logrus.Debugf("Discovering external drivers in %s", stdDriverDir)
-	if _, err := os.Stat(stdDriverDir); err == nil {
-		if err := discoverDriversInDir(stdDriverDir); err != nil {
-			logrus.Warnf("Error discovering external drivers in %q: %v", stdDriverDir, err)
-		}
-	}
-
 	if driverPaths := os.Getenv("LIMA_DRIVERS_PATH"); driverPaths != "" {
 		paths := filepath.SplitList(driverPaths)
 		for _, path := range paths {
@@ -137,6 +124,17 @@ func discoverDrivers() error {
 		}
 	}
 
+	stdDriverDir, err := usrlocalsharelima.LibexecLima()
+	if err != nil {
+		return err
+	}
+
+	logrus.Debugf("Discovering external drivers in %s", stdDriverDir)
+	if _, err := os.Stat(stdDriverDir); err == nil {
+		if err := discoverDriversInDir(stdDriverDir); err != nil {
+			logrus.Warnf("Error discovering external drivers in %q: %v", stdDriverDir, err)
+		}
+	}
 	return nil
 }
 

website/content/en/docs/dev/drivers.md

@@ -40,8 +40,8 @@ This creates external driver binaries in `_output/libexec/lima/` with the naming
 
 Lima discovers external drivers from these locations:
 
-1. **Standard directory**: `<LIMA-PREFIX>/libexec/lima/`, where `<LIMA_PREFIX>` is the location path where the Lima binary is present
-2. **Custom directories**: Set path to the external driver's directory via `LIMA_DRIVERS_PATH` environment variable
+1. **Custom directories**: Set path to the external driver's directory via `LIMA_DRIVERS_PATH` environment variable
+2. **Standard directory**: `<LIMA-PREFIX>/libexec/lima/`, where `<LIMA_PREFIX>` is the location path where the Lima binary is present
 
 The discovery process is handled by [`pkg/registry/registry.go`.](https://github.com/lima-vm/lima/blob/master/pkg/registry/registry.go)