navsection: userguide
title: "Mounting Keep as a filesystem"
...
+{% comment %}
+Copyright (C) The Arvados Authors. All rights reserved.
+
+SPDX-License-Identifier: CC-BY-SA-3.0
+{% endcomment %}
This tutoral describes how to access Arvados collections using traditional filesystem tools by mounting Keep as a read-only file system using @arv-mount@.
* You can browse, open and read Keep entries as if they are regular files.
* It is easy for existing tools to access files in Keep.
-* Data is downloaded on demand. It is not necessary to download an entire file or collection to start processing.
+* Data is streamed on demand. It is not necessary to download an entire file or collection to start processing.
-The default mode permits browsing any collection in Arvados as a subdirectory under the mount directory. To avoid having to fetch a potentially large list of all collections, collection directories only come into existence when explicitly accessed by their Keep locator. For instance, a collection may be found by its content hash in the @keep/by_id@ directory.
+The default mode permits browsing any collection in Arvados as a subdirectory under the mount directory. To avoid having to fetch a potentially large list of all collections, collection directories only come into existence when explicitly accessed by UUID or portable data hash. For instance, a collection may be found by its content hash in the @keep/by_id@ directory.
<notextile>
<pre><code>~$ <span class="userinput">mkdir -p keep</span>
The last line unmounts Keep. Subdirectories will no longer be accessible.
-Within each directory on Keep, there is a @.arvados#collection@ file that does not show up with @ls@. Its contents include, for instance, the @portable_data_hash@, which is the same as the Keep locator.
+In the top level directory of each collection, arv-mount provides a special file called @.arvados#collection@ that contains a JSON-formatted API record for the collection. This can be used to determine the collection's @portable_data_hash@, @uuid@, etc. This file does not show up in @ls@ or @ls -a@.
+
+h3. Modifying files and directories in Keep
+
+By default, all files in the Keep mount are read only. However, @arv-mount --read-write@ enables you to perform the following operations using normal Unix command line tools (@touch@, @mv@, @rm@, @mkdir@, @rmdir@) and your own programs using standard POSIX file system APIs:
+
+* Create, update, rename and delete individual files within collections
+* Create and delete subdirectories inside collections
+* Move files and directories within and between collections
+* Create and delete collections within a project (using @mkdir@ and @rmdir@ in a project directory)
+
+Not supported:
+
+* Symlinks, hard links
+* Changing permissions
+* Extended attributes
+* Moving a subdirectory of a collection into a project, or moving a collection from a project into another collection
+
+If multiple clients (separate instances of arv-mount or other arvados applications) modify the same file in the same collection within a short time interval, this may result in a conflict. In this case, the most recent commit wins, and the "loser" will be renamed to a conflict file in the form @name~YYYYMMDD-HHMMSS~conflict~@.
+
+Please note this feature is in beta testing. In particular, the conflict mechanism is itself currently subject to race conditions with potential for data loss when a collection is being modified simultaneously by multiple clients. This issue will be resolved in future development.
projects / arvados.git / blobdiff