Don't use 'stack' in static but use $USER.
diff --git a/files/swift-proxy-server.conf b/files/swift-proxy-server.conf
index 9a3b54b..6b7dd52 100644
--- a/files/swift-proxy-server.conf
+++ b/files/swift-proxy-server.conf
@@ -1,6 +1,6 @@
 [DEFAULT]
 bind_port = 8080
-user = stack
+user = %USER%
 log_facility = LOG_LOCAL1
 
 [pipeline:main]