For sftp, set virtual servers to home dir only, but root for all

Hi I each of my virtual sites logs into sftp port 2222 fine, and only sees their homedir. they can't navigate to /etc which is great

now, I would like a master or root login so that I am able to edit any sites files

for example, a customer will phone me up and ask me to change something in their .html

I would like to do this without logging in as them.

On my previous hosting prvoider, I would do this via a "master ftp" login



Can you not login via SFTP as root ? That should work by default, unless it has been locked down to disallow root logins.