diff --git a/Setting-up-a-Hub.md b/Setting-up-a-Hub.md
index 742d2b2..fdce2f3 100644
--- a/Setting-up-a-Hub.md
+++ b/Setting-up-a-Hub.md
@@ -2,7 +2,7 @@
 
 ### create an aws instance
 
-We recommend a `c5.4xlarge` instance or equivalent (16 vCPU, 32G RAM, 500GB SSD drive)
+We recommend a `c5.4xlarge` instance or equivalent (16 vCPU, 32G RAM, 500GB SSD drive) running Ubuntu 20.04 LTS
 
 (As a benchmark, on Nov 13, 2022 this setup used 350 gigs of disk space.)