On the backup server, in directory /onapp/templates, there are a lot of files of strange / unfamiliar names like b4rnx5z4jrxk41_20150119100943. What they are used for? Can we delete them?
Release OnApp 3.x
Files similar to b4rnx5z4jrxk41_20150119100943 are custom templates.
In order to determine templates that are in use you could run the following database command:
mysql> select id, label from templates where file_name='xxxxx';
Where file_name would be the file you are checking.
You can then compare this template to see if it is in use by a Virtual Machine with:
mysql> select id, identifier, hostname, label from virtual_machines where template_id=xx;>
where template_id is the id from the first command. If the template is not in use by a Virtual Machine, it can be safely deleted.