setup: WriteToFile primitive

Add a new `WriteToFile` primitive plus a usecase for it.

Signed-off-by: Simon de Vlieger <supakeen@redhat.com>

modify.go

@@ -15,15 +15,13 @@ func EmptyRootPassword(prefix string) error {
 }
 
 func EnableSystemRequest(prefix string) error {
-	//579 # Enable System Request debugging of the kernel
-	//580 if [ "$SYSRQ" != "" ]; then
-	//581     echo "= Enabling System Request debugging of the kernel."
-	//582     cat >> ${PREFIX}/etc/sysctl.d/arm-image-installer-sysrq.conf <<-EOH
-	//583         # Controls the System Request debugging functionality of the kernel
-	//584         kernel.sysrq = 1
-	//585     EOH
-	//586 fi
-	return nil
+	path := filepath.Join(prefix, "etc/sysctl.d/posadka-sysrq.conf")
+
+	// TODO, might want an append instead?
+	return WriteToFile(
+		path,
+		[]byte("kernel.sysrq = 1\n"),
+	)
 }
 
 func ShowBoot(prefix string) error {
@@ -39,6 +37,4 @@ func ShowBoot(prefix string) error {
 		[]byte("rhgb quiet "),
 		[]byte(""),
 	)
-
-	return nil
 }

primitive.go

@@ -29,3 +29,7 @@ func ReplaceInFile(path string, a, b []byte) error {
 
 	return nil
 }
+
+func WriteToFile(path string, data []byte) error {
+	return os.WriteFile(path, data, 0644)
+}