diff a/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java b/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java
--- a/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java
+++ b/src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java
@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.  Oracle designates this
@@ -32,13 +32,21 @@
 public class UnixSystem {
 
     private native void getUnixInfo();
 
     // Warning: the following 4 fields are used by Unix.c
+
+    /** The current username. */
     protected String username;
+
+    /** The current user ID. */
     protected long uid;
+
+    /** The current group ID. */
     protected long gid;
+
+    /** The current list of groups. */
     protected long[] groups;
 
     /**
      * Instantiate a {@code UnixSystem} and load
      * the native library to access the underlying system information.
