[Upgrade Assistant] No bulk option to mark multiple legacy indices as verified_read_only

[lma456]

I want to upgrade to Elasticsearch 9.0 and prepare my cluster by marking legacy indices (created before 8.0) as verified_read_only so they do not need to be reindexed.

The documentation states that marking indices as read-only is a valid alternative to reindexing them, provided I don't need to write to them anymore.

However, the only supported way to set verified_read_only is through the Kibana Upgrade Assistant UI, where I must click "Mark as read-only" for each index individually.

In large clusters with hundreds or thousands of legacy indices, this becomes practically impossible.

I also tried:

index.blocks.write = true → not sufficient to suppress warnings

Upgrade Assistant Batch Reindex API → only supports reindexing, not read-only

What is missing:

There is currently:

No bulk UI action to mark multiple indices as verified_read_only

No public, documented API to mark indices that way

No CLI tool or migration-assistance endpoint that works cluster-wide

This issue directly impacts upgrade usability for large clusters.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[dakrone]

There is currently:
No bulk UI action to mark multiple indices as verified_read_only
No public, documented API to mark indices that way

The add index block API supports comma-separated or wildcard patterns for adding the verified-read-only block to an index or multiple indices.

On the UI side, I suggest opening an issue in https://github.com/elastic/kibana/issues which handles the UI aspects of the upgrade assistant.

[lma456]

PUT /index/_settings
{
  "index.verified_read_only": true
}

This is not currently working

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "can not update private setting [index.verified_read_only]; this setting is managed by Elasticsearch"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "can not update private setting [index.verified_read_only]; this setting is managed by Elasticsearch"
  },
  "status": 400
}

Any fixes for this?

[nielsbauman]

@lma456 as @dakrone suggested, you should use the add index block API:

PUT /index/_block/read_only

I just verified that that adds the index.verified_read_only setting to the index. I'm going to close this for now, as ES does provide an API to mark indices as read-only in bulk. Feel free to reopen this issue if you do believe there is functionality missing (or misbehaving) in ES.

[lma456]

This was not enough for me. Instead i had to remove the old read only flag

PUT /index-*/_settings
{
  "index.blocks.read_only": false,
  "index.blocks.read_only_allow_delete": false,
  "index.blocks.write": false
}

Then the add index block api worked for me

PUT /index-*/_block/write

Thanks for your help!