OpenSearch/docs/reference/setup/upgrade.asciidoc

[[setup-upgrade]]
== Upgrading Elasticsearch

[IMPORTANT]
===========================================
Before upgrading Elasticsearch:

* Consult the <<breaking-changes,breaking changes>> docs.
* Test upgrades in a dev environment before upgrading your production cluster.
* Always <<modules-snapshots,back up your data>> before upgrading.
  You **cannot roll back** to an earlier version unless you have a backup of your data.
* If you are using custom plugins, check that a compatible version is available.
===========================================

Elasticsearch can usually be upgraded using a rolling upgrade process,
resulting in no interruption of service.  This section details how to perform
both rolling upgrades and upgrades with full cluster restarts.

To determine whether a rolling upgrade is supported for your release, please
consult this table:

[cols="1<m,1<m,3",options="header",]
|=======================================================================
|Upgrade From   |Upgrade To     |Supported Upgrade Type
|< 5.x          |6.x            |<<reindex-upgrade,Reindex to upgrade>>
|5.x            |5.y            |<<rolling-upgrades,Rolling upgrade>> (where `y > x`)
|5.x            |6.x            |<<restart-upgrade,Full cluster restart>>
|6.0.0 pre GA   |6.x            |<<restart-upgrade,Full cluster restart>>
|6.x            |6.y            |<<rolling-upgrades,Rolling upgrade>> (where `y > x`)
|=======================================================================

[IMPORTANT]
.Indices created in Elasticsearch 2.x or before
===============================================

Elasticsearch is able to read indices created in the *previous major version
only*.  For instance, Elasticsearch 6.x can use indices created in
Elasticsearch 5.x, but not those created in Elasticsearch 2.x or before.

This condition also applies to indices backed up with
<<modules-snapshots,snapshot and restore>>.  If an index was originally
created in 2.x, it cannot be restored into a 6.x cluster even if the
snapshot was made by a 5.x cluster.

Elasticsearch 6.x nodes will fail to start in the presence of too old indices.

See <<reindex-upgrade>> for more information about how to upgrade old indices.
===============================================


include::rolling_upgrade.asciidoc[]

include::cluster_restart.asciidoc[]

include::reindex_upgrade.asciidoc[]