Add note that some services require a minimal config.yml to start.

no issue #

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <peter.amstutz@curii.com>

diff --git a/doc/admin/upgrading.html.textile.liquid b/doc/admin/upgrading.html.textile.liquid
index b04c5cf4244bbeab6611d929250b3f651507514c..23d71204385af2e8d7a7a9ae17514b7223bea9c8 100644 (file)
--- a/doc/admin/upgrading.html.textile.liquid
+++ b/doc/admin/upgrading.html.textile.liquid
@@ -48,7 +48,17 @@ Arvados 2.0 is a major upgrade, with many changes.  Please read these upgrade no
 
 h3. Migrating to centralized config.yml
 
-See "Migrating Configuration":config-migration.html for notes on migrating legacy per-component configuration files to the new centralized @/etc/arvados/config.yml@.  To ensure a smooth transition, the per-component config files continue to be read, and take precedence over the centralized configuration.
+See "Migrating Configuration":config-migration.html for notes on migrating legacy per-component configuration files to the new centralized @/etc/arvados/config.yml@.
+
+To ensure a smooth transition, the per-component config files continue to be read, and take precedence over the centralized configuration.  Your cluster should continue to function after upgrade but before doing the full configuration migration.  However, several services (keepstore, keep-web, keepproxy) require a minimal `/etc/arvados/config.yml` to start:
+
+<pre>
+Clusters:
+  zzzzz:
+    Services:
+      Controller:
+        ExternalURL: "https://zzzzz.example.com"
+</pre>
 
 h3. Keep-balance configuration migration