diff --git a/Makefile b/Makefile
index 2c20101..988cb3b 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,9 @@
 PACKAGE	= Probe
 VERSION	= 0.0.2
 SUBDIRS	= data src tools
-RM	= rm -f
-LN	= ln -f
-TAR	= tar -czvf
+RM	?= rm -f
+LN	?= ln -f
+TAR	?= tar -czvf
 
 
 all: subdirs
diff --git a/data/Makefile b/data/Makefile
index 8cc1b8d..cb9d4e2 100644
--- a/data/Makefile
+++ b/data/Makefile
@@ -1,8 +1,8 @@
 PREFIX	= /usr/local
 DESTDIR	=
-MKDIR	= mkdir -p
-INSTALL	= install
-RM	= rm -f
+MKDIR	?= mkdir -p
+INSTALL	?= install
+RM	?= rm -f
 
 
 all:
diff --git a/src/Makefile b/src/Makefile
index 0424867..cd005ae 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -3,16 +3,16 @@ PREFIX	= /usr/local
 DESTDIR	=
 BINDIR	= $(PREFIX)/bin
 CC	= cc
-CPPFLAGSF=
-CPPFLAGS=
+CPPFLAGSF?=
+CPPFLAGS?=
 CFLAGSF	= -W `pkg-config --cflags libApp`
 CFLAGS	= -Wall -g -O2 -pedantic
 LDFLAGSF= `pkg-config --libs libApp`
 LDFLAGS	= 
-RM	= rm -f
-LN	= ln -f
-MKDIR	= mkdir -p
-INSTALL	= install
+RM	?= rm -f
+LN	?= ln -f
+MKDIR	?= mkdir -p
+INSTALL	?= install
 
 
 all: $(TARGETS)