Add standlone migration procedure

Closes #624

Creates a new page under install-deploy-manage Operator docs.
This page summarizes the changes that led to the deprecation of the Gateway/Filesystem.
It overviews the steps required to create a new Single-Node, Single-Drive deployment
with the contents, settings, and IAM policies from the old deployment.

Author: djwfyi

source/operations/install-deploy-manage/migrate-fs-gateway.rst

@@ -0,0 +1,107 @@
+.. _minio-gateway-migration:
+
+=======================================
+Migrate from Gateway or Filesystem Mode
+=======================================
+
+.. default-domain:: minio
+
+.. contents:: Table of Contents
+   :local:
+   :depth: 1
+
+Background
+----------
+
+The MinIO Gateway entered a feature freeze in July 2020.
+In February 2022, MinIO announced the `deprecation of the MinIO Gateway <https://blog.min.io/deprecation-of-the-minio-gateway/?ref=docs>`__.
+Along with the deprecation announcement, MinIO also announced that the feature would be removed in six months time.
+
+As of :minio-release:`RELEASE.2022-10-29T06-21-33Z`, the MinIO Gateway and the related filesystem mode code have been removed.
+Deployments still using the `standalone` or `filesystem` MinIO modes that upgrade to :minio-release:`RELEASE.2022-10-29T06-21-33Z` or later receive an error when attempting to start MinIO.
+
+Overview
+--------
+
+To upgrade to a :minio-release:`RELEASE.2022-10-29T06-21-33Z` or later, those who were using the `standalone` or `filesystem` deployment modes must create a new :ref:`Single-Node Single-Drive <minio-snsd>` deployment and migrate settings and content to the new deployment.
+
+This document outlines the steps required to successfully launch and migrate to a new deployment.
+
+Procedure
+---------
+
+#. Retrieve the existing deployment's **environment variables**
+
+   Use :mc-cmd:`mc admin config get` with the ``--json`` flag to retrieve a list of the environment variables defined on the existing standalone MinIO deployment.
+
+#. :ref:`Create a new Single-Node Single-Drive MinIO deployment <minio-snsd>`
+
+   The location of the deployment can be any empty folder on the storage medium of your choice.
+   As long as the existing deployment is not to the root of a drive, a new folder on the same drive can work for the new deployment.
+   If the existing standalone system points to the root of the drive, you must use a separate drive for the new deployment.
+
+   Use the environment variable values retrieved from the standalone deployment to establish the same values for the new deployment.
+
+   Set the port to a custom point different than the existing standalone deployment.
+
+#. Duplicate **configurations** from existing standalone deployment to new deployment
+
+
+
+#. Duplicate **buckets** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc ls` with the ``--json`` flag to retrieve a list of the buckets that exist on the standalone deployment.
+   Use the list to recreate the buckets on the new deployment.
+
+#. Duplicate **tiers** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc admin tier ls` with the ``--json`` flag to retrieve a list of the tiers that exist on the standalone deployment.
+   Use the list to recreate the tiers on the new deployment.
+
+#. Duplicate **policies** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc admin policy list` with the ``--json`` flag  to retrieve a list of policies that exist on the standalone deployment.
+   Use the list to recreate the policies on the new deployment.
+
+#. Duplicate **groups** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc admin group list` with the ``--json`` flag to retrieve a list of groups that exist on the standalone deployment.
+   Use the list to recreate the groups on the new deployment.
+
+#. Duplicate **users** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc admin user list` with the ``--json`` flag to retrieve a list of users with access key, policy name, and status.
+   Use the list to recreate the users on the new deployment.
+
+   Note: You will need to define each user's ``SECRETKEY`` on the new deployment.
+   Make note of the ``SECRETKEY`` for each user to let them know their new credentials.
+
+#. Duplicate **service accounts** from existing standalone deployment to new deployment
+
+   Use :mc-cmd:`mc admin user svcacct ls` with the ``--json`` flag to list existing service accounts on the standalone deployment.
+   Use the list to recreate the service accounts on the new deployment.
+
+#. Use :mc:`mc mirror` with the ``--watch`` flag on the standalone deployment to move objects to the new |SNSD| deployment
+
+   Do this for each bucket.
+
+#. After the initial mirror process completes, convert standalone deployment to be read only
+
+   Some options for doing this include:
+
+   - ``mc admin policy remove`` for each active policy
+   - ``mc admin policy unset`` to remove policy/policies for each group
+
+#. Wait for ``mc mirror`` to complete for all buckets.
+
+#. Shut down the server for the existing standalone deployment.
+
+   
+
+#. Restart the new MinIO deployment with the ports used for the previous standalone deployment.
+
+
+
+#. Confirm the new deployment works as expected.
+
+   Verify that users and service accounts have access to the buckets and objects as usual.