add copyright notice

diff --git a/web/index.txt b/web/index.txt
index e3b0c95c8108caff1831e3c2a269b2389fa92267..6f3e1f6de4ecd416d99ba3af4526496af1377500 100644 (file)
--- a/web/index.txt
+++ b/web/index.txt
@@ -335,4 +335,5 @@ Robert Morris (rtm@mit.edu)
 
 You can reach all of us at 6.828-staff@pdos.csail.mit.edu.
 
-
+xv6 and lecture notes are copyright © 2006-present by Russ Cox,
+Frans Kaashoek, and Robert Morris.