Update PG migration runbook

doc/postgres/migration.md

@@ -210,7 +210,7 @@ sudo -u postgres pg_list_replication_subscriptions
 
 #### 11.1 Stop writes on old primary
 
-(app maintenance mode, stop app/daemons)
+Put app(s) in maintenance mode, stop the app/daemons.
 
 ---
 
@@ -242,13 +242,20 @@ sudo -u postgres pg_fix_sequences [db_name]
 
 #### 11.4 Point app to NEW_HOST
 
-* Update pg.kosmos.local in /etc/hosts on app server(s) (maybe override
+1. Update `pg.kosmos.local` in `/etc/hosts` on app server(s). For example:
-  attribute for role and converge)
+
-* Start app/daemons, deactivate maintenance mode
+   ```bash
+   export NEW_PG_PRIMARY=[private_ip]
+   bundle exec knife ssh roles:ejabberd -a knife_zero.host "sudo sed -r \"s/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\s(pg.kosmos.local)/$NEW_PG_PRIMARY\t\1/\" -i /etc/hosts"
+   ```
+
+   Or override node attribute(s) if necessary and/or approporiate.
+
+2. Start the app/daemons, and deactivate maintenance mode.
 
 ---
 
-### 🧹 12. CLEANUP (NEW_HOST)
+### 🧹 12. CLEANUP NEW_HOST
 
 ```bash
 sudo -u postgres pg_drop_replication_subscriptions
@@ -256,7 +263,7 @@ sudo -u postgres pg_drop_replication_subscriptions
 
 ---
 
-### 🧹 13. CLEANUP (PRIMARY)
+### 🧹 13. CLEANUP PRIMARY
 
 TODO: Looks like slots are dropped automatically, when subscriptions are dropped
 
@@ -266,6 +273,15 @@ sudo -u postgres pg_drop_replication_publications
 
 ---
 
+### 🧹 13. CLEANUP Chef
+
+Once all apps/databases are migrated, update the role in the node
+config of the new primary to 'postgres_primary' and converge it.
+
+Also delete the old primary node config from the Chef repo.
+
+---
+
 ### ✅ DONE
 
 ---