feat: add support for dashboard custom console parameter

Fixes #12070

Signed-off-by: Pranav <pranavppatil767@gmail.com>
Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

Author: Pranav

internal/app/machined/pkg/system/services/dashboard.go

@@ -9,6 +9,10 @@ import (
 	"context"
 	"fmt"
 	"strconv"
+	"strings"
+
+	"github.com/siderolabs/go-pointer"
+	"github.com/siderolabs/go-procfs/procfs"
 
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/system/events"
@@ -25,18 +29,57 @@ import (
 // the required methods.
 type Dashboard struct{}
 
+// getCustomConsole returns the custom console parameter value if specified, empty string otherwise.
+func (d *Dashboard) getCustomConsole() string {
+	consoleParam := procfs.ProcCmdline().Get(constants.KernelParamDashboardConsole).First()
+
+	return pointer.SafeDeref(consoleParam)
+}
+
+// hasCustomConsole checks if a custom console is specified via kernel parameter.
+func (d *Dashboard) hasCustomConsole() bool {
+	return d.getCustomConsole() != ""
+}
+
+// getConsoleDevice returns the console device path to use for the dashboard.
+func (d *Dashboard) getConsoleDevice() (string, error) {
+	consoleName := d.getCustomConsole()
+
+	if consoleName != "" {
+		// Validate that the console name starts with "tty"
+		if !strings.HasPrefix(consoleName, "tty") || strings.Contains(consoleName, "/") {
+			return "", fmt.Errorf("invalid console name %q: must start with 'tty'", consoleName)
+		}
+
+		return fmt.Sprintf("/dev/%s", consoleName), nil
+	}
+
+	// Default to the standard dashboard TTY
+	return fmt.Sprintf("/dev/tty%d", constants.DashboardTTY), nil
+}
+
 // ID implements the Service interface.
 func (d *Dashboard) ID(_ runtime.Runtime) string {
 	return "dashboard"
 }
 
 // PreFunc implements the Service interface.
 func (d *Dashboard) PreFunc(_ context.Context, _ runtime.Runtime) error {
+	// Skip TTY switching if a custom console is specified
+	if d.hasCustomConsole() {
+		return nil
+	}
+
 	return console.Switch(constants.DashboardTTY)
 }
 
 // PostFunc implements the Service interface.
 func (d *Dashboard) PostFunc(_ runtime.Runtime, _ events.ServiceState) error {
+	// Skip TTY switching if a custom console is specified
+	if d.hasCustomConsole() {
+		return nil
+	}
+
 	return console.Switch(constants.KernelLogsTTY)
 }
 
@@ -57,7 +100,10 @@ func (d *Dashboard) Volumes(runtime.Runtime) []string {
 
 // Runner implements the Service interface.
 func (d *Dashboard) Runner(r runtime.Runtime) (runner.Runner, error) {
-	tty := fmt.Sprintf("/dev/tty%d", constants.DashboardTTY)
+	tty, err := d.getConsoleDevice()
+	if err != nil {
+		return nil, fmt.Errorf("failed to determine console device: %w", err)
+	}
 
 	return restart.New(process.NewRunner(false, &runner.Args{
 		ID:          d.ID(r),

pkg/machinery/constants/constants.go

@@ -87,6 +87,9 @@ const (
 	// KernelParamDashboardDisabled is the kernel parameter name for disabling the dashboard.
 	KernelParamDashboardDisabled = "talos.dashboard.disabled"
 
+	// KernelParamDashboardConsole is the kernel parameter name for specifying the dashboard console.
+	KernelParamDashboardConsole = "talos.dashboard.console"
+
 	// KernelParamEnvironment is the kernel parameter name for passing process environment.
 	KernelParamEnvironment = "talos.environment"
 

website/content/v1.12/reference/kernel.md

@@ -257,6 +257,28 @@ Kernel logs will be sent to the currently active console and the dashboard will
 
 It is set to be `1` by default on SBCs.
 
+#### `talos.dashboard.console`
+
+By default, the Talos dashboard runs on `/dev/tty2` with automatic TTY switching.
+You can specify a custom console device for the dashboard using this parameter.
+
+For example, to run the dashboard on a serial console:
+
+```text
+talos.dashboard.console=ttyS0
+```
+
+When this parameter is specified:
+
+* The dashboard will run on `/dev/ttyS0`
+* TTY switching will be disabled (no automatic switching between tty1 and tty2)
+* The console name must start with "tty"
+
+This is useful for headless servers or systems where you want the dashboard accessible through a serial console connection.
+
+> Note: If Talos dashboard is set to use ttyS0, make sure that Linux kernel command line doesn't include
+> `console=ttyS0` or similar, as it will conflict with the dashboard output.
+
 #### `talos.environment`
 
 Each value of the argument sets a default environment variable.