Stanford README: update ansible commands

playbooks/edx-west/README.md

-Readme
-------
+# Stanford Ansible Configuration Files
 
 This directory has the live playbooks that we use here at Stanford to
 maintain our instance of OpenEdX at [class.stanford.edu][c].  We check
@@ -23,25 +22,28 @@ Other install docs:
   [1]: https://docs.google.com/document/d/1ZDx51Jxa-zffyeKvHmTp_tIskLW9D9NRg9NytPTbnrA/edit#heading=h.iggugvghbcpf
 
 
-Ansible Commands - Prod
------------------------
+## Ansible Commands - Prod
 
 Generally we do installs as the "ubuntu" user.  You want to make
 sure that the stanford-deploy-20130415 ssh key is in your ssh agent.
 
-    ANSIBLE_CONFIG=prod-ansible.cfg ANSIBLE_EC2_INI=ec2.ini ansible-playbook prod-log.yml -u ubuntu -c ssh -i ./ec2.py
+    ANSIBLE_CONFIG=prod-ansible.cfg ANSIBLE_EC2_INI=prod-ec2.ini ansible-playbook prod-app.yml -e "machine=app4" -u ubuntu -c ssh -i ./ec2.py
 
+Some specifics:
 
-Ansible Commands - Stage
-------------------------
+* To hit multiple machines the -e parameter would look like this: ```"machine=app(1|2|4)"```.
 
-Verify that you're doing something reasonable:
+* Usually I do with the ```--list-hosts``` option first to verify that I'm
+  doing something sane before actually running.
 
-    ANSIBLE_CONFIG=stage-ansible.cfg ANSIBLE_EC2_INI=ec2.ini ansible-playbook stage-app.yml -u ubuntu -c ssh -i ./ec2.py --list-hosts
+* To do the utility machines, use ```prod-worker.yml```.  Those also
+  take the machine variable.
 
-Verify that you're doing something reasonable:
 
-    ANSIBLE_CONFIG=stage-ansible.cfg ANSIBLE_EC2_INI=ec2.ini ansible-playbook stage-app.yml -u ubuntu -c ssh -i ./ec2.py
+## Ansible Commands - Stage
 
+Command is:
+
+    ANSIBLE_CONFIG=stage-ansible.cfg ANSIBLE_EC2_INI=stage-ec2.ini ansible-playbook stage-app.yml -e "machine=app1" -u ubuntu -c ssh -i ./ec2.py