howto/cumin.md

@@ -197,6 +197,16 @@ and will simply show which hosts match the request:
 [briefly described in the Wikimedia docs]: https://wikitech.wikimedia.org/wiki/Cumin#PuppetDB_host_selection
 [parallel-ssh]: https://code.google.com/archive/p/parallel-ssh/
 
+## Mangling host lists for Cumin consumption
+
+Say you have a list of hosts, separated by newlines. You want to run a
+command on all those hosts. You need to pass the list as
+comma-separated words instead.
+
+Use the `paste` command:
+
+    cumin "$(paste -sd, < host-list.txt)" "uptime"
+
 ## Disabling touch confirmation
 
 If running a command that takes longer than a few seconds, the