X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/0bd1c28bed9a0756c61037947d5a9dccd5066f00..5b3187552676947ee74e4b652e7a04d3d9b9a3a4:/doc/user/tutorials/tutorial-keep-mount.html.textile.liquid

diff --git a/doc/user/tutorials/tutorial-keep-mount.html.textile.liquid b/doc/user/tutorials/tutorial-keep-mount.html.textile.liquid
index e07be5d907..43af024df2 100644
--- a/doc/user/tutorials/tutorial-keep-mount.html.textile.liquid
+++ b/doc/user/tutorials/tutorial-keep-mount.html.textile.liquid
@@ -14,19 +14,43 @@ h2. 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.
+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.
 
 <notextile>
 <pre><code>~$ <span class="userinput">mkdir -p keep</span>
 ~$ <span class="userinput">arv-mount keep</span>
-~$ <span class="userinput">cd keep/c1bad4b39ca5a924e481008009d94e32+210</span>
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">ls</span>
+~$ <span class="userinput">cd keep/by_id/c1bad4b39ca5a924e481008009d94e32+210</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">ls</span>
 var-GS000016015-ASM.tsv.bz2
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">md5sum var-GS000016015-ASM.tsv.bz2</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">md5sum var-GS000016015-ASM.tsv.bz2</span>
 44b8ae3fde7a8a88d2f7ebd237625b4f  var-GS000016015-ASM.tsv.bz2
-~/keep/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">cd ../..</span>
+~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">cd ../..</span>
 ~$ <span class="userinput">fusermount -u keep</span>
 </code></pre>
 </notextile>
+
+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.
+
+h3. Modifying files and directories in Keep
+
+By default, all files in the Keep mount are read only.  However, @arv-mount --enable-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 condiditions with potential for data loss when a collection is being modified simultaneously by multiple clients.  This issue will be resolved in future development.