Implement qemu-system stderr log passthrough

cmd/root.go

@@ -68,7 +68,7 @@ func init() {
 	rootCmd.AddCommand(versionCmd)
 	rootCmd.AddCommand(copyrightCmd)
 
-	rootCmd.PersistentFlags().BoolVar(&vmDebugFlag, "vm-debug", false, "Enables the VM debug mode. This will open an accessible VM monitor. You can log in with root user and no password.")
+	rootCmd.PersistentFlags().BoolVar(&vmDebugFlag, "vm-debug", false, "Enables the VM debug mode. This will open an accessible VM monitor and enable direct QEMU command log passthrough. You can log in with root user and no password.")
 	rootCmd.PersistentFlags().BoolVar(&unrestrictedNetworkingFlag, "vm-unrestricted-networking", false, "Enables unrestricted networking. This will allow the VM to connect to the internet.")
 	rootCmd.PersistentFlags().Uint32Var(&vmMemAllocFlag, "vm-mem-alloc", defaultMemAlloc, fmt.Sprintf("Specifies the VM memory allocation in KiB. (the default is %v in LUKS mode)", defaultMemAllocLUKS))
 	rootCmd.PersistentFlags().Uint32Var(&vmOSUpTimeoutFlag, "vm-os-up-timeout", 30, "Specifies the VM OS-up timeout in seconds.")

cmd/utils.go

@@ -206,7 +206,7 @@ func runVM(passthroughArg string, fn runvm.Func, forwardPortsRules []vm.PortForw
 		OSUpTimeout:  time.Duration(vmOSUpTimeoutFlag) * time.Second,
 		SSHUpTimeout: time.Duration(vmSSHSetupTimeoutFlag) * time.Second,
 
-		ShowDisplay: vmDebugFlag,
+		Debug: vmDebugFlag,
 	}
 
 	vi, err := vm.NewVM(slog.Default().With("caller", "vm"), vmCfg)

imgbuilder/imgbuilder.go

@@ -43,7 +43,7 @@ type BuildContext struct {
 	vi *vm.VM
 }
 
-func NewBuildContext(logger *slog.Logger, baseISOPath string, outPath string, showVMDisplay bool, biosPath string) (*BuildContext, error) {
+func NewBuildContext(logger *slog.Logger, baseISOPath string, outPath string, debug bool, biosPath string) (*BuildContext, error) {
 	baseISOPath = filepath.Clean(baseISOPath)
 	outPath = filepath.Clean(outPath)
 
@@ -73,7 +73,7 @@ func NewBuildContext(logger *slog.Logger, baseISOPath string, outPath string, sh
 		MemoryAlloc: 512,
 
 		UnrestrictedNetworking: true,
-		ShowDisplay:            showVMDisplay,
+		Debug:                  debug,
 		InstallBaseUtilities:   true,
 	})
 	if err != nil {

vm/cfg.go

@@ -115,7 +115,7 @@ func configureBaseVMCmd(logger *slog.Logger, cfg Config) (string, []qemucli.Arg,
 		args = append(args, biosArg)
 	}
 
-	if !cfg.ShowDisplay {
+	if !cfg.Debug {
 		args = append(args, qemucli.MustNewStringArg("display", "none"))
 	}
 

vm/vm.go

@@ -22,6 +22,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"sync"
 	"sync/atomic"
@@ -99,7 +100,7 @@ type Config struct {
 	SSHUpTimeout time.Duration
 
 	// Mostly debug-related options.
-	ShowDisplay          bool
+	Debug                bool // This will show the display and forward all QEMU warnings/errors to stderr.
 	InstallBaseUtilities bool
 }
 
@@ -176,6 +177,10 @@ func NewVM(logger *slog.Logger, cfg Config) (*VM, error) {
 	stderrBuf := bytes.NewBuffer(nil)
 	cmd.Stderr = stderrBuf
 
+	if cfg.Debug {
+		cmd.Stderr = io.MultiWriter(cmd.Stderr, os.Stderr)
+	}
+
 	// This function is OS-specific.
 	osspecifics.SetNewProcessGroupCmd(cmd)