Upgrade from 7.17 guide (elastic#3398)

This PR adds a new ad-hoc document to guide users to upgrade from 7.17.x
to 9.x, which requires two major upgrades plus upgrading all ingest
components and clients between the upgrades.

It supports all deployment types, covers orchestrator upgrades, etc.

This new document builds upon and links to the existing upgrade
documentation.

Its purpose is to bring together all relevant upgrade steps and
considerations into a single, end-to-end guide that walks through what
would normally be an exercise each user performs independently when
planning a full stack upgrade, considering the specifics of this upgrade
path.

It is not intended to introduce new upgrade procedures or instructions,
as these should already be accurately documented in the existing upgrade
guides.

Closes elastic/docs-content-internal#387

---------

Co-authored-by: shainaraskas <[email protected]>

Author: 2 people

deploy-manage/toc.yml

@@ -807,7 +807,7 @@ toc:
           - file: upgrade/prepare-to-upgrade/upgrade-assistant.md
       - file: upgrade/deployment-or-cluster.md
         children:
-          - hidden: upgrade/deployment-or-cluster/upgrade-717.md
+          - file: upgrade/deployment-or-cluster/upgrade-717.md
           - file: upgrade/deployment-or-cluster/upgrade-on-ech.md
           - file: upgrade/deployment-or-cluster/upgrade-on-ece.md
           - file: upgrade/deployment-or-cluster/upgrade-on-eck.md

deploy-manage/upgrade.md

@@ -48,6 +48,10 @@ Upgrading your Elastic cluster or deployment involves several stages, including
 
 - [Upgrade ingest components](./upgrade/ingest-components.md): Covers supporting components such as {{beats}}, {{agent}}, {{ls}}, and APM Server.
 
+:::{note}
+If you’re still running {{stack}} version 7.17 or earlier, refer to the [Upgrade from 7.17 guide](/deploy-manage/upgrade/deployment-or-cluster/upgrade-717.md) for detailed guidance on planning and executing the upgrade to the latest {{version.stack}} release.
+:::
+
 Additionally, if you're using a self-managed orchestration platform such as {{ece}} or {{eck}}, refer to [Upgrade your ECE or ECK orchestrator](/deploy-manage/upgrade/orchestrator.md) to keep the orchestrator up to date.
 
 ## Availability during upgrades
@@ -97,3 +101,12 @@ If you're upgrading to the current {{version.stack}} release from an earlier 8.x
 For flexible upgrade scheduling, 8.19 {{agent}}, {{beats}}, and {{ls}} are compatible with all 9.x versions of {{es}}.
 
 By default, 8.x {{es}} clients are compatible with 9.x and use [REST API compatibility](elasticsearch://reference/elasticsearch/rest-apis/compatibility.md) to maintain compatibility with the 9.x cluster.
+
+### Upgrade paths from 7.17 [upgrade-paths-7.x]
+
+Upgrading from {{stack}} version 7.17 to the latest {{version.stack}} release involves two major upgrades:
+
+- From 7.17 to 8.19
+- From 8.19 to {{version.stack}}
+
+For detailed guidance on planning and executing these upgrades, refer to the [Upgrade from 7.17 guide](/deploy-manage/upgrade/deployment-or-cluster/upgrade-717.md).

deploy-manage/upgrade/deployment-or-cluster.md

@@ -29,6 +29,8 @@ This section contains the upgrade instructions for {{es}} clusters and {{kib}} i
 
 Before proceeding with the upgrade, review the [Plan your upgrade](/deploy-manage/upgrade/plan-upgrade.md) guidance to understand compatibility and timing considerations, and follow the steps in [Prepare to upgrade](/deploy-manage/upgrade/prepare-to-upgrade.md) to get your environment ready for the upgrade.
 
+If you’re still running {{stack}} version 7.17 or earlier, refer to the [Upgrade from 7.17 guide](/deploy-manage/upgrade/deployment-or-cluster/upgrade-717.md) for detailed guidance on planning and executing the upgrade to the latest {{version.stack}} release.
+
 ## Out-of-order releases [out-of-order-releases]
 
 Elastic maintains several minor versions of {{es}} at the same time. This means releases do not always happen in order of their version numbers. You can only upgrade to {{version.stack}} if the version you are currently running meets both of these conditions:

deploy-manage/upgrade/deployment-or-cluster/_snippets/upgrade-validation.md

@@ -0,0 +1,15 @@
+After completing the upgrade, verify that your system is fully operational. Check that data ingestion and search are working as expected, clients and integrations can connect, and {{kib}} is accessible.
+
+Confirm that the cluster is healthy and reports the expected version. You can use the following APIs to validate the cluster status after the upgrade:
+
+* Check cluster health
+  ```console
+  GET _cluster/health?pretty
+  ```
+  Ensure the status is green, or yellow if that is expected for your configuration (for example, in single-node clusters).
+
+* Check nodes and version
+  ```console
+  GET _cat/nodes?v&h=name,node.role,master,ip,version
+  ```
+  Verify that all nodes report the upgraded version in the version column.