How could I reset the Splunk admin password?

To reset the admin password you will need to have access to the file system:
– move the $SPLUNK_HOME/etc/passwd file to passwd.bak
– restart splunk. After the restart you should be able to login using the default login                 (admin/changeme).

If you created other user accounts, copy those entries from the backup file into the new passwd file and restart splunk.