Models

A model is an environment associated with a controller. When a controller is created two models are provisioned along with it. These initial models are named ‘controller’ and ‘default’. The ‘controller’ model is for internal Juju management and is not intended for general workloads. The ‘default’ model, however, is ready for immediate use. Further workload models can be added at any time.

In v.2.6.0, a user-added model can be hosted by a cloud that is different than the one that hosts the two default models (‘controller’ and ‘default’). A controller thus has the possibility of being “multi-cloud”.

Model management

Common model management tasks are summarised below.

The most important ones are Adding a model and Configuring models.

Add a model

Models can be added easily to a controller.

The Adding a model page provides a full explanation and includes examples.

Change models

Use the switch command to change from one model to another:

Running the command with no arguments will return the currently active controller and model:

juju switch

To change to a model:

juju switch foo
Selects the last used model in controller 'foo' (if the latter exists), otherwise model 'foo' in the current controller.

juju switch :foo
Selects model 'foo' in the current controller.

juju switch foo:bar
Selects model 'bar' in controller 'foo'.

juju switch foo:
Selects the last used model in controller 'foo'

For command line help and syntax run juju help switch.

Compare a bundle to a model

An operator can compare a model with a charm bundle. This is useful for determining what has changed since the bundle was deployed or just how a model differs from a bundle that was not yet used.

This topic is covered on the Charm bundles page.

Configure a model

Configuration can occur at the model level. This will affect all Juju machines in the model. For instance, a logging level and API port can be stipulated.

See the Configuring models page for explanations.

Cross model relations

Traditionally, when adding a relation between two applications (see Charm relations) the applications reside within the same model and controller. It is possible to overcome this limitation by employing cross model relations.

This topic is covered on the Cross model relations page.

Destroy a model

When a model is destroyed all associated applications and machines are also destroyed. It is a very destructive process.

Disable commands

It is possible to curtail command use for Juju users on a per-model basis.

The Disabling commands page gives more information.

Examine a model

Use the show-model command to examine a specific model.

For command line help and syntax run juju help show-model.

List all models

Use the models command to list all models for a controller.

For command line help and syntax run juju help models.

Manage user access

If you're using multiple Juju users you will need to manage access to your models. See page Working with multiple users for a full explanation.

Migrate models

Model can be migrated from one controller to another. Model migration is useful when upgrading a controller and for load balancing.

For a complete explanation see the Migrating models page.

SSH access

SSH access can be provided to all machines, present and future, on a per-model basis.

For in-depth coverage see page Machine authentication.

Set constraints for a model

Charm constraints can be managed at the model level. This will affect all charms used in the model unless overridden. Constraints are used to select minimum requirements for any future machines Juju may create.

This subject is covered on page Setting constraints for a model.

Upgrade a model

Juju software is upgraded at the model level with the upgrade-model command. This affects the Juju agents running on every machine Juju creates. This does not pertain to the Juju software package installed on a client system.

See Upgrading models for complete coverage.

View logs

Use the debug-log command to examine logs on a per-model basis. This allows inspection of activities occurring on multiple Juju machines simultaneously. Due to the expected large volume of data, advanced filtering is available.

A full explanation is provided on the Juju logs page.

View model status

Use the status command to view the status of a model.

For command line help and syntax run juju help status.

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