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Services MUST provide the main metainfo.xml file which provides important metadata about the service. 
Apart from that, other files can be provided to give more information about the service. More details about these files are provided below.

A service may also inherit from either a previous stack version or common services.  For more information see the Service Inheritance page.

metainfo.xml

In the metainfo.xml service descriptor, one can first define the service and its components.

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• config-type - String representing a group of configurations. Example: core-site, hdfs-site, yarn-site, etc. When configurations are saved in Ambari, they are persisted within a version of config-type which is immutable. If you change and save HDFS core-site configs 4 times, you will have 4 versions of config-type core-site. Also, when a service's configs are saved, only the changed config-types are updated.
• configFiles - lists the config-files handled by the enclosing component
• configFile - represents one config-file of a certain type
  
  • type - type of file based on which contents are generated differently
    
    • xml - XML file generated in Hadoop friendly format. Ex: hdfs-site.xml
    • env - Generally used for scripts where the content value is used as a template. The template has config-tags whose values are populated at runtime during file generation. Ex: hadoop-env.sh
    • properties - Generates property files where entries are in key=value format. Ex: falcon-runtime.properties
  • dictionaryName - Name of the config-type as which key/values of this config file will be stored
• configuration-dependencies - Lists the config-types on which this component or service depends on. One of the implications of this dependency is that whenever the config-type is updated, Ambari automatically marks the component or service as requiring restart. From the code section above, whenever core-site is updated, both HDFS service as well as HDFS_CLIENT component will be marked as requiring restart.
• configuration-dir - Directory where files listed in configFiles will be. Optional. Default value is configuration.

Adding new configs in a config-type

There are a number of different parameters that can be specified to a config item when it is added to a config-type. These have been covered here. 

UI - Categories

Configurations defined above show up in the service's Configs page.

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Ambari is capable of enabling and disabling Kerberos for a cluster. To inform Ambari of the identities and configurations to be used for the service and its components, each service can provide a kerberos.json file.

Read more about the Kerberos support in the Automated Kerberization wiki page and the Kerberos Descriptor descriptor in the Kerberos Descriptor documentation.

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Any custom stack must include these two JSON files.  For further information see the Stack Properties wiki page.

Services

Each stack-version includes services which are either referenced from common-services, or defined inside the stack-version's services folder. 
Services are defined in common-services if they will be shared across multiple stacks. If they will never be shared, then they can be defined inside the stack-version.

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