sets the location of the debian backports package mirror that will be used to fetch packages in order to build the live system. By default, this points to http://backports.debian.org/debian-backports/.
sets the location of the debian package mirror that should end up configured in the final image and which is the one a user would see and use. This has not necessarily to be the same that is used to build the image, e.g. if you use a local mirror but want to have an official mirror in the image. By default, 'http://http.debian.net/debian/' is used.
sets the location of the debian package mirror that should end up configured in the final image and which is the one a user would see and use. This has not necessarily to be the same that is used to build the image, e.g. if you use a local mirror but want to have an official mirror in the image. By default, 'http://httpredir.debian.org/debian/' is used.
sets the location of the debian security package mirror that should end up configured in the final image. By default, 'http://security.debian.org/' is used.