It is possible to mirror other instances of a site, as backup, assuming that you will just pull from them and that they will be kept read-only denying the access from the webserver (read: no not add a virtual host for them, to avoid conflicts on editing).

The purpose here is just backup.

  • create a site on the mirroring instance.

  • go into repo/<newid>, e.g. repo/backup

  • remove it (it's empty anyway)

  • clone via git the mirrored site keeping the same name. E.g. git clone git:// backup

  • add a cronjob which executes: script/ <newid> <remote-name>, e.g. script/ backup origin