=== Setting changes

==== Command line flags

Command line flags using single dash notation must be now specified as the first arguments.
For example if previously using:

[source,sh]
---------------
./elasticsearch --node.name=test_node -Des.path.conf=/opt/elasticsearch/conf/test_node
---------------

This will now need to be changed to:

[source,sh]
---------------
./elasticsearch -Des.path.conf=/opt/elasticsearch/conf/test_node --node.name=test_node
---------------

for the flag to take effect.

[[migration-script-settings]]
==== Scripting settings

The `script.disable_dynamic` node setting has been replaced by fine-grained
script settings described in the <<enable-dynamic-scripting,scripting docs>>.
The following setting previously used to enable dynamic or inline scripts:

[source,yaml]
---------------
script.disable_dynamic: false
---------------

It should be replaced with the following two settings in `elasticsearch.yml` that
achieve the same result:

[source,yaml]
---------------
script.inline: on
script.indexed: on
---------------

==== Units required for time and byte-sized settings

Any settings which accept time or byte values must now be specified with
units.  For instance, it is too easy to set the `refresh_interval` to 1
*millisecond* instead of 1 second:

[source,js]
---------------
PUT _settings
{
  "index.refresh_interval": 1
}
---------------

In 2.0, the above request will throw an exception. Instead the refresh
interval should be set to `"1s"` for one second.

==== Merge and merge throttling settings

The tiered merge policy is now the only supported merge policy. These settings
have been removed:

* `index.merge.policy.type`
* `index.merge.policy.min_merge_size`
* `index.merge.policy.max_merge_size`
* `index.merge.policy.merge_factor`
* `index.merge.policy.max_merge_docs`
* `index.merge.policy.calibrate_size_by_deletes`
* `index.merge.policy.min_merge_docs`
* `index.merge.policy.max_merge_docs`

Merge throttling now uses a feedback loop to auto-throttle.  These settings
have been removed:

* `indices.store.throttle.type`
* `indices.store.throttle.max_bytes_per_sec`
* `index.store.throttle.type`
* `index.store.throttle.max_bytes_per_sec`

==== Shadow replica settings

The `node.enable_custom_paths` setting has been removed and replaced by the
`path.shared_data` setting to allow shadow replicas with custom paths to work
with the security manager. For example, if your previous configuration had:

[source,yaml]
------
node.enable_custom_paths: true
------

And you created an index using shadow replicas with `index.data_path` set to
`/opt/data/my_index` with the following:

[source,js]
--------------------------------------------------
PUT /my_index
{
  "index": {
    "number_of_shards": 1,
    "number_of_replicas": 4,
    "data_path": "/opt/data/my_index",
    "shadow_replicas": true
  }
}
--------------------------------------------------

For 2.0, you will need to set `path.shared_data` to a parent directory of the
index's data_path, so:

[source,yaml]
-----------
path.shared_data: /opt/data
-----------

==== Resource watcher settings renamed

The setting names for configuring the resource watcher have been renamed
to prevent clashes with the watcher plugin

* `watcher.enabled` is now `resource.reload.enabled`
* `watcher.interval` is now `resource.reload.interval`
* `watcher.interval.low` is now `resource.reload.interval.low`
* `watcher.interval.medium` is now `resource.reload.interval.medium`
* `watcher.interval.high` is now `resource.reload.interval.high`

==== Hunspell dictionary configuration

The parameter `indices.analysis.hunspell.dictionary.location` has been
removed, and `<path.conf>/hunspell` is always used.

==== CORS allowed origins

The CORS allowed origins setting, `http.cors.allow-origin`, no longer has a default value. Previously, the default value
was `*`, which would allow CORS requests from any origin and is considered insecure. The `http.cors.allow-origin` setting
should be specified with only the origins that should be allowed, like so:

[source,yaml]
---------------
http.cors.allow-origin: /https?:\/\/localhost(:[0-9]+)?/
---------------

==== JSONP support

JSONP callback support has now been removed. CORS should be used to access Elasticsearch
over AJAX instead:

[source,yaml]
---------------
http.cors.enabled: true
http.cors.allow-origin: /https?:\/\/localhost(:[0-9]+)?/
---------------

==== In memory indices

The `memory` / `ram` store (`index.store.type`) option was removed in
Elasticsearch.  In-memory indices are no longer supported.

==== Log messages truncated

Log messages are now truncated at 10,000 characters. This can be changed in
the `logging.yml` configuration file with the `file.layout.conversionPattern`
setting.

Remove mapping.date.round_ceil setting for date math parsing #8889 (issues: #8556, #8598)

==== Custom config file

It is no longer possible to specify a custom config file with the `CONF_FILE`
environment variable, or the `-Des.config`, `-Des.default.config`, or
`-Delasticsearch.config` parameters.

Instead, the config file must be named `elasticsearch.yml` and must be located
in the default `config/` directory, or in the directory specified in the
`CONF_DIR` environment variable.

==== `ES_CLASSPATH removed`

The `ES_CLASSPATH` environment variable is no longer used to set the class
path. External libraries should preferably be loaded using the plugin
mechanism or, if you really must, be copied to the `lib/` directory.