fix up constraints to be used during bootstrap

src/en/charms-constraints.md

@@ -75,26 +75,23 @@ In the event that a constraint cannot be met, the unit will not be deployed.
 
 !!! Note: 
     Constraints work on an "or better" basis: If you ask for 4 CPUs, you 
-    may get 8, but you won't get 2
+    may get 8, but you won't get 2.
+
+## Setting constraints for a controller
 
+Constraints can be applied to a controller during its creation
+(`juju bootstrap` command) by using the `--bootstrap-constraints` option. See
+[Creating a controller][controllers-creating] for details and examples.
 
-
-## Using constraints when creating a controller
+## Setting default model constraints
 
-A controller is created using the `bootstrap` command, which accepts a 
-'--constraints' switch to specify which machine to use. When you create the
-controller with constraints, the same constraints apply to each subsequent 
-machine created, so setting constraints on the controller is the same as making
-global constraints. These can of course be overriden by constraints at the
-model, application or machine level as detailed below.
+Default model constraints can be set during the controller-creation process by
+using the `--constraints` option (with the `juju bootstrap` command). See
+[Creating a controller][controllers-creating] for more information on how to do
+this.
 
-Example:
-
-Creating a new AWS controller to use a particular amount of memory:
-
-```bash
-juju bootstrap aws mycloud --constraints mem=4G
-```
+Default model constraints can be overridden for specific models, applications,
+or machines, as detailed below.
 
 ## Setting constraints for a model
 
@@ -111,8 +108,8 @@ least 4 gigabytes of memory. You can check the current constraints with:
 juju get-model-constraints
 ```
 
-As with similar commands, you can 'unset' the constraint by setting its value to
-null:
+As with similar commands, you can 'unset' the constraint by setting its value
+to null:
 
 ```bash
 juju set-model-constraints mem=
@@ -121,7 +118,6 @@ juju set-model-constraints mem=
 Model-related constraints can also be overridden at the application and machine
 level.
 
-
 ## Setting constraints for an application
 
 Usually, constraints for an application are set at deploy time, by passing the 
@@ -176,3 +172,8 @@ the '--to' placement switch -
     Juju's knowledge of the available spaces on the underlying cloud may lag
     behind recent changes. To force Juju to re-examine the spaces it can use,
     you should run the command `juju reload-spaces`.  
+
+
+<!-- LINKS -->
+
+[controllers-creating]: ./controllers-creating.html

src/en/controllers-creating.md

@@ -29,22 +29,22 @@ itself, are known as **model constraints**. These are set via the
 known as **controller constraints** and are set by using the
 `--bootstrap-constraints` option. The same values can be used by either type.
 
-For more details on constraints, see [Constraints][constraints].
+For general information on constraints, see [Constraints][constraints].
 
 ## Examples
 
-### Set minimum specifications for all machines in a controller's models
+### Set default model constraints for a given controller
 
-Below, all machines in the LXD controller's models will have at
-least 4GiB of memory:
+Below, all machines in the LXD controller's models will have at least 4GiB of
+memory:
 
 ```bash
 juju bootstrap --constraints="mem=4G" localhost
 ```
 
-### Set minimum specifications for a new controller
+### Set controller constraints for a new controller
 
-This example shows how to request at least 4GiB of memory and two CPUs for a
+This example shows how to request at least 4GiB of memory and two CPUs for an
 AWS controller:
 
 ```bash