apt repo for duo ( https://duo.com/docs/duounix )

Change-Id: If2e5fea3cb7cb7cbbc2ea4041dad287f1214174b
diff --git a/linux/system/repo/duo.yml b/linux/system/repo/duo.yml
new file mode 100644
index 0000000..95db543
--- /dev/null
+++ b/linux/system/repo/duo.yml
@@ -0,0 +1,12 @@
+classes:
+- system.linux.system.repo.keystorage.duo
+parameters:
+  _param:
+    linux_system_repo_duo_url: http://pkg.duosecurity.com/Ubuntu
+  linux:
+    system:
+      repo:
+        duo:
+          key: ${_param:linux_system_repo_duo_key}
+          source: "deb [arch=amd64] ${_param:linux_system_repo_duo_url} ${_param:linux_system_codename} main"
+          architectures: amd64