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Service Configuration

When deploying a service, the charm you use will often support or even require specific configuration options to be set.

Juju provides tools to help manage these options and respond to changes over the lifetime of the service deployment. These options apply to the entire service, as opposed to only a specific unit or relation. The configuration can modified by an administrator at deployment time or after the services are operational.

Discovering service configuration options

You can discover what configuration options are available for a specific charm in various ways

  • By running the juju get <service> command.
  • By viewing the charm in the charm store.
  • By examining the config.yaml file in the charm itself.

The configurations setting names and the values they take will obviously vary between charms. The options and possible values are all well documented however, so you should consult one of the above sources to find out particular details.

Configuring a service at deployment

It is possible to set configuration values when deploying a service by providing a yaml-formatted file containing configuration values.

For example, upon investigation we discover that the Mediawiki charm allows us to set values for the name of the wiki and the 'skin' to use. We can put these inside a configuration file.

  name: Juju Wiki
  skin: monobook
  admins: admin:admin

We can then use this configuration when we deploy the service:

juju deploy --config myconfig.yaml mediawiki

Caution: If the yaml configuration file cannot be read or contains some syntax errors or invalid options, you will receive an error message to this effect. However, the service will still be deployed .

Configuring a service which is already deployed

It is possible to set or change configuration of a service which is already deployed.

Before you set any of these options, you may want to check what current options are already set, using the juju get <service> command. For example:

juju get mediawiki

Should return something like this:

charm: mediawiki
service: mediawiki
    default: true
    description: Admin users to create, user:pass
    type: string
    value: null
    default: true
    description: turn on debugging features of mediawiki
    type: boolean
    value: false
    default: true
    description: URL to fetch logo from
    type: string
    value: null
    default: true
    description: The name, or Title of the Wiki
    type: string
    value: Please set name of wiki
    default: true
    description: skin for the Wiki
    type: string
    value: vector

You can set the options using the juju set <service>, specifying multiple key=value pairs if necessary:

juju set mediawiki skin=monoblock name='Juju Wiki'

Setting options back to their default value is done using the unset command followed by the service and the respective options:

juju unset mediawiki admins name