Removing things

This page is devoted to the topic of removing objects in Juju. We first cover the meanings of certain removal terms and then provide information and steps for how different kinds of objects are removed.

For guidance on what to do when a removal does not apply cleanly consult the Troubleshooting removals page.

Removal terms

There is a distinction between the similar sounding terms "unregister", "detach", "remove", "destroy", and "kill". These terms are ordered such that their effect increases in severity:

  • Unregister means to decouple a resource from a logical entity for the client. The affect is local to the client only and does not affect the logical entity in any way.

  • Detach means to decouple a resource from a logical entity (such as an application). The resource will remain available and the underlying cloud resources used by it also remain in place.

  • Remove means to cleanly remove a single logical entity. This is a destructive process, meaning the entity will no longer be available via Juju, and any underlying cloud resources used by it will be freed (however, this can often be overridden on a case-by-case basis to leave the underlying cloud resources in place).

  • Destroy means to cleanly tear down a logical entity, along with everything within these entities. This is a vary destructive process.

  • Kill means to forcibly tear down an unresponsive logical entity, along with everything within it. This is a very destructive process that does not guarantee associated resources are cleaned up.

Object removal list

Destroying controllers

A controller is removed with:

juju destroy-controller <controller-name>

You will always be prompted to confirm this action. Use the -y option to override this.

As a safety measure, if there are any models (besides the 'controller' model) associated with the controller you will need to pass the --destroy-all-models option.

Additionally, if there is persistent storage in any of the controller's models you will be prompted to either destroy or release the storage, using the --destroy-storage or --release-storage options respectively.

For example:

juju destroy-controller -y --destroy-all-models --destroy-storage aws

Use the kill-controller command as a last resort if the controller is not accessible for some reason:

juju kill-controller <controller-name>

In this case, the controller will be removed by communicating directly with the cloud provider. Any other Juju machines residing within any of the controller's models will not be destroyed and will need to be removed manually using provider tools/console. This command will first attempt to mimic the behaviour of the destroy-controller command and failover to the more drastic mode if that attempt fails.

Destroying models

To destroy a model, along with any associated machines and applications:

juju destroy-model <model-name>

You will always be prompted to confirm this action. Use the -y option to override this.

Additionally, if there is persistent storage in the model you will be prompted to either destroy or release the storage, using the --destroy-storage or --release-storage options respectively.

For example:

juju destroy-model -y --destroy-storage beta

Detaching storage

To detach a storage instance:

juju detach-storage <storage-instance>

For example:

juju detach-storage osd-devices/2

Detaching storage does not destroy the storage.

Removing applications

An application can be removed with:

juju remove-application <application-name>

For example:

juju remove-application apache2

This will remove all of the application's units. All associated machines will also be removed providing they are not hosting containers or another application's units.

If persistent storage is in use by the application it will be detached and left in the model. However, the --destroy-storage option can be used to instruct Juju to destroy the storage once detached.

Removing an application which has relations with another application will terminate that relation. This may adversely affect the other application. See section Removing relations below for how to selectively remove relations.

Removing machines

A machine can be removed with:

juju remove-machine <machine ID>

For example:

juju remove-machine 3

However, it is not possible to remove a machine that is currently hosting either a unit or a container. Either remove all of its units (or containers) first or, as a last resort, use the --force option.

By default, when a machine is removed, the backing system, typically a cloud instance, is also destroyed. The --keep-instance option overrides this; it allows the instance to be left running.

Removing relations

A relation is removed by calling out both (application) sides of the relation:

juju remove-relation <application-name> <application-name>

For example:

juju remove-relation mediawiki mysql

In cases where there is more than one relation between the two applications, it is necessary to specify the interface at least once:

juju remove-relation mediawiki mysql:db

Removing storage

To remove a storage instance from a model first detach it and then:

juju remove-storage <storage-instance>

For example:

juju detach-storage osd-devices/3
juju remove-storage osd-devices/3

The --force option can be used to avoid having to first detach the storage.

The removal of storage is, by default, a destructive process (destroyed on the cloud provider). To prevent this, the --no-destroy option is available. Note that, by using this option, the storage will no longer be visible to Juju.

Removing units

To remove individual units instead of the entire application (i.e. all the units):

juju remove-unit <unit>

For example:

juju remove-unit postgresql/2

In the case that the removed unit is the only one running the corresponding machine will also be removed unless any of the following is true for that machine:

  • it was created with juju add-machine
  • it is not being used as the only controller
  • it is not hosting Juju-managed containers (KVM guests or LXD containers)

To remove multiple units:

juju remove-unit mediawiki/1 mediawiki/3 mediawiki/5 mysql/2

The --destroy-storage option is available for this command as it is for the remove-application command above.

Removing users

A user can be removed from a controller with:

juju remove-user <user-name>

For example:

juju remove-user teo

Unregistering controllers

A controller can be removed from a client with:

juju unregister <controller-name>

For example:

juju unregister aws-controller

This removes local connection information from the local client. This command does not affect the controller itself in any way.

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