updated readme with details about backend

README.md

@@ -1,2 +1,20 @@
 # terraform
 
+The terraform code for my small personal infrastructure
+
+## Backend
+
+I use the pg backend on a PostgreSQL hosted on my NAS. Create the user (named
+`terraform`) and database (`terraform_backend`) for it. The user's password is
+managed with `pass`.
+
+```sh
+pass generate pg.monotremata.xyz/terraform
+psql -u pg.monotremata.xyz
+```
+
+```sql
+CREATE DATABASE terraform_backend;
+CREATE USER terraform WITH ENCRYPTED PASSWORD '****';
+GRANT ALL PRIVILEGES ON DATABASE terraform_backend TO terraform;
+```