---
layout: default
navsection: userguide
title: "Mounting Keep as a filesystem"
...

This tutoral describes how to access Arvados collections using traditional filesystem tools by mounting Keep as a read-only file system using @arv-mount@.

{% include 'tutorial_expectations' %}

h2. Arv-mount

@arv-mount@ provides several features:

* 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.

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/by_id/c1bad4b39ca5a924e481008009d94e32+210</span>
~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">ls</span>
var-GS000016015-ASM.tsv.bz2
~/keep/by_id/c1bad4b39ca5a924e481008009d94e32+210$ <span class="userinput">md5sum var-GS000016015-ASM.tsv.bz2</span>
44b8ae3fde7a8a88d2f7ebd237625b4f  var-GS000016015-ASM.tsv.bz2
~/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.