`serve s3` implements a basic s3 server that serves a remote via s3.
This can be viewed with an s3 client, or you can make an [s3 type
remote](/s3/) to read and write to it with rclone.

`serve s3` is considered **Experimental** so use with care.

S3 server supports Signature Version 4 authentication. Just use
`--auth-key accessKey,secretKey` and set the `Authorization`
header correctly in the request. (See the [AWS
docs](https://docs.aws.amazon.com/general/latest/gr/signature-version-4.html)).

`--auth-key` can be repeated for multiple auth pairs. If
`--auth-key` is not provided then `serve s3` will allow anonymous
access.

Please note that some clients may require HTTPS endpoints. See [the
SSL docs](#ssl-tls) for more information.

This command uses the [VFS directory cache](#vfs-virtual-file-system).
All the functionality will work with `--vfs-cache-mode off`. Using
`--vfs-cache-mode full` (or `writes`) can be used to cache objects
locally to improve performance.

Use `--force-path-style=false` if you want to use the bucket name as a
part of the hostname (such as mybucket.local)

Use `--etag-hash` if you want to change the hash uses for the `ETag`.
Note that using anything other than `MD5` (the default) is likely to
cause problems for S3 clients which rely on the Etag being the MD5.

### Quickstart

For a simple set up, to serve `remote:path` over s3, run the server
like this:

```
rclone serve s3 --auth-key ACCESS_KEY_ID,SECRET_ACCESS_KEY remote:path
```

This will be compatible with an rclone remote which is defined like this:

```
[serves3]
type = s3
provider = Rclone
endpoint = http://127.0.0.1:8080/
access_key_id = ACCESS_KEY_ID
secret_access_key = SECRET_ACCESS_KEY
use_multipart_uploads = false
```

Note that setting `disable_multipart_uploads = true` is to work around
[a bug](#bugs) which will be fixed in due course.

### Bugs

When uploading multipart files `serve s3` holds all the parts in
memory. This is a limitaton of the library rclone uses for serving S3
and will hopefully be fixed at some point.

### Limitations

`serve s3` will treat all directories in the root as buckets and
ignore all files in the root. You can use `CreateBucket` to create
folders under the root, but you can't create empty folders under other
folders not in the root.

When using `PutObject` or `DeleteObject`, rclone will automatically
create or clean up empty folders. If you don't want to clean up empty
folders automatically, use `--no-cleanup`.

When using `ListObjects`, rclone will use `/` when the delimiter is
empty. This reduces backend requests with no effect on most
operations, but if the delimiter is something other than `/` and
empty, rclone will do a full recursive search of the backend, which
can take some time.

Versioning is not currently supported.

Metadata will only be saved in memory other than the rclone `mtime`
metadata which will be set as the modification time of the file.

### Supported operations

`serve s3` currently supports the following operations.

- Bucket
    - `ListBuckets`
    - `CreateBucket`
    - `DeleteBucket`
- Object
    - `HeadObject`
    - `ListObjects`
    - `GetObject`
    - `PutObject`
    - `DeleteObject`
    - `DeleteObjects`
    - `CreateMultipartUpload`
    - `CompleteMultipartUpload`
    - `AbortMultipartUpload`
    - `CopyObject`
    - `UploadPart`

Other operations will return error `Unimplemented`.