+Each Arvados installation is identified by a cluster identifier, which is a unique 5-character lowercase alphanumeric string. There are 36 5 = 60466176 possible cluster identifiers.
+
+* For automated test purposes, use “z****”
+* For experimental/local-only/private clusters that won’t ever be visible on the public Internet, use “x****”
+* For long-lived clusters, we recommend reserving a cluster id. Contact "info@curii.com":mailto:info@curii.com for more information.
+
+Here is one way to make a random 5-character string: