A Xilinx boot image format (BIF) file is used to specify the subsystem images in the PDI and the subsystem image partitions. Each separate file within a subsystem image is stored in one of the subsystem image partitions. The BIF file is a data file in ASCII format. The BIF file tells Bootgen how to create the PDI by processing each of the input files.
Command line users must modify the Vivado-generated BIF and run Bootgen to create the PDI from the instructions in the BIF files. You can optionally write your own BIF file and specify the Vivado generated PDI along with other input files to extend the PDI. Vitis IDE users can use a wizard to specify the required inputs for the BIF file, and then use the Vitis IDE to create the BIF file and run Bootgen to create the PDI.