+Crunch dispatches work from the job queue on the Arvados API server. Before you start installing the Crunch dispatcher, now's a good time to check that the API server and Git server can coordinate to create job records. Run these commands *on your shell server* to create a collection, and a job to calculate the MD5 checksum of every file in it:
+
+<notextile>
+<pre><code>~$ <span class="userinput">echo 'Hello, Crunch!' | arv-put --portable-data-hash -</span>
+…
+d40c7f35d80da669afb9db1896e760ad+49
+~$ <span class="userinput">read -rd $'\000' newjob <<EOF; arv job create --job "$newjob"
+{"script_parameters":{"input":"d40c7f35d80da669afb9db1896e760ad+49"},
+ "script_version":"0988acb472849dc0",
+ "script":"hash",
+ "repository":"arvados"}
+EOF</span>
+</code></pre>
+</notextile>
+
+If you get the error
+
+<pre>
+ArgumentError: Specified script_version does not resolve to a commit
+</pre>
+
+it often means that the API server can't read the specified repository—either because it doesn't exist, or because the user running the API server doesn't have permission to read the repository files. Check the API server's log (@/var/www/arvados-api/current/log/production.log@) for details, and double-check the instructions in the "Git server installation guide":install-arv-git-httpd.html.
+
+If everything goes well, the API server should create a job record, and your @arv@ command will output the JSON for that record. It should have state @Queued@ and script_version @0988acb472849dc08d576ee40493e70bde2132ca@. If the job JSON includes those fields, you can proceed to install the Crunch dispatcher and a compute node. This job will remain queued until you install those services.