[CentOS] BackupPC problem - wrong user

I recently moved BackupPC from CentOS-6 to CentOS-7.
But when I browse to localhost/BackupPC I'm told
  Error: Wrong user: my userid is 48[apache], instead of 984(backuppc)

As far as I can tell, the BackupPC settings are exactly the same
as they were before the move.

It seems htttpd is running the program as user apache
rather than backuppc, as required.
Is there a simple setting in /etc/httpd/ that will tell httpd
to run as a different user?


-- 
Timothy Murphy  
gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin