If you want to perform some action before altering a domain (creation, alteration, or deletion) you may specify a command to run here. If multiple actions are to be performed the command to run can be a script. The command has access to special environment variables specific to the domain, such as VIRTUALSERVER_DOM, VIRTUALSERVER_IP, VIRTUALSERVER_USER, VIRTUALSERVER_HOME, VIRTUALSERVER_PASS, and more. Any variable found in the /etc/webmin/virtual-server/domains/$DOM file will be available as an environment variable.