Document the extended s3.list-objects-v1 flag in a new Ceph section

doc/030_preparing_a_new_repo.rst

@@ -339,6 +339,39 @@ For example with an actual endpoint:
 
     $ restic -o s3.bucket-lookup=dns -o s3.region=oss-eu-west-1 -r s3:https://oss-eu-west-1.aliyuncs.com/bucketname init
 
+Ceph
+****
+
+`Ceph Object Gateway <https://ceph.io/ceph-storage/object-storage/>`__ is an object
+storage interface built on top of librados to provide applications with a RESTful
+gateway to Ceph Storage Clusters.
+
+Ceph Rados Gateway (RGW) provides a S3 interface that is compatible with a large
+subset of the Amazon S3 RESTful API.
+
+You will need to setup the following environment variables with the proper credentials:
+
+.. code-block:: console
+
+    $ export AWS_ACCESS_KEY_ID=<YOUR-ACCESS-KEY-ID>
+    $ export AWS_SECRET_ACCESS_KEY=<YOUR-SECRET-ACCESS-KEY>
+
+Now you can easily initialize restic to use Ceph RGW as a backend with
+this command.
+
+.. code-block:: console
+
+    $ restic -r s3://<RGW-S3-ENDPOINT>/<RGW-S3-BUCKET> init
+    enter password for new backend:
+    enter password again:
+    created restic backend xxxxxxxxxx at s3://<RGW-S3-ENDPOINT>/<RGW-S3-BUCKET>
+    Please note that knowledge of your password is required to access
+    the repository. Losing your password means that your data is irrecoverably lost.
+
+.. note:: Version of Ceph before v14.2.5 do not implement the ListObjectsV2 API properly.
+          On these backends you need to provide the ``-o s3.list-objects-v1=true`` option
+          to use the ListObjects API instead.
+
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