debugd: Allow root login on serial console when using debug image (#407)

debugd/cmd/debugd/debugd.go

@@ -43,6 +43,10 @@ func main() {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
+	if err := deploy.DeleteUserPassword(ctx, "root"); err != nil {
+		log.Errorf("root login: %w")
+	}
+
 	download := deploy.New(log.Named("download"), &net.Dialer{}, serviceManager, streamer)
 	var fetcher metadata.Fetcher
 	csp := os.Getenv("CONSTEL_CSP")

debugd/internal/debugd/deploy/seriallogin.go

@@ -0,0 +1,18 @@
+package deploy
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+)
+
+// DeleteUserPassword sets the user's password to an empty string
+// effectively allowing anyone with access to the serial console to log in.
+func DeleteUserPassword(ctx context.Context, user string) error {
+	cmd := exec.CommandContext(ctx, "passwd", "-d", user)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("deleting user password: %q %w", output, err)
+	}
+	return nil
+}