diff --git a/core/common.sh b/core/common.sh
index 7e3094b..829752f 100644
--- a/core/common.sh
+++ b/core/common.sh
@@ -1,9 +1,16 @@
 #!/bin/bash
 # ------------------------------------------------------------------------------
 # Common printing functions for all installer scripts.
+# Dual output: colores ANSI a stdout + texto plano (sin codigos) a $LOG_FILE.
+# El log es AUXILIAR: su fallo de escritura no debe abortar la operacion
+# (p. ej. log root-owned + doctor sin root) — por eso el append va guardado.
 # ------------------------------------------------------------------------------
 
-print_step() { echo -e "\n\033[1;34m>>>\033[0m \033[1m$1\033[0m"; }
-print_substep() { echo -e "\033[1;32m  =>\033[0m $1"; }
-print_warning() { echo -e "\033[1;33m  [AVISO]\033[0m $1"; }
-print_error() { echo -e "\033[1;31m  [ERROR]\033[0m $1"; }
+LOG_FILE="${LOG_FILE:-install.log}"
+
+_log_plain() { printf '%s\n' "$1" >> "$LOG_FILE" 2>/dev/null || true; }
+
+print_step()    { echo -e "\n\033[1;34m>>>\033[0m \033[1m$1\033[0m"; _log_plain "";    _log_plain ">>> $1"; }
+print_substep() { echo -e "\033[1;32m  =>\033[0m $1";                 _log_plain "  => $1"; }
+print_warning() { echo -e "\033[1;33m  [AVISO]\033[0m $1";            _log_plain "  [AVISO] $1"; }
+print_error()   { echo -e "\033[1;31m  [ERROR]\033[0m $1";            _log_plain "  [ERROR] $1"; }