I have spent 3 days wrestling with this and getting no where.
Whatever I do in virtualmin, webmin or usermin I get a lock filename error.
Failed to create virtual server : Lock filename contains invalid characters
Failed to delete user : Lock filename contains invalid characters
I also get the same error when I run the post-install config. When it gets to setting the primary nameserver it returns:
Lock filename contains invalid characters
I have tried deleting/renaming lock files - no joy.
I have been through the logs and can’t find any indication of which lock file is causing the issue. There are no other webmin instances running and no other users logged in. I am using the latest version of webmin/virtualmin.