Plesk Backup Error: ‘ERROR Unable to open /opt/psa/var/apspkgarc/archive-index.xml’
I was getting the following error when trying to use Plesk’s backup function:
ERROR Unable to open /opt/psa/var/apspkgarc/archive-index.xml
The solution is to visit the “Application Vault” under the “Server” tab of your Plesk interface. The file gets auto-generated at that point.
For more information on how to use Plesk’s backup feature, read this post