Did you create a Cloud instance of Jira? If so, you can log in to your instance with your Atlassian account details. Resetting password will send an email to your Atlassian account email address.
If you're using a Server version, the SMTP server have to be configured and enabled to receive emails. If you lost your admin account, there's a backup from SQL procedure available here: https://confluence.atlassian.com/jira/retrieving-the-jira-administrator-192836.html
Please note that Jira 7+ does not use HSQL anymore but uses H2 DB if you did not change it for another db type.
Hope this helps!
I’m a designer on the Jira team. For a long time, I’ve fielded questions from other designers about how they should be using Jira Software with their design team. I’ve also heard feedback from other ...
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