Why is my Linux reporting an allowable size error when building an .ISO?

You should add these parameters to the command:

-no-emul-boot -boot-load-size 4 -boot-info-table

The parameters are:

• no-emul-boot: Specifies that the boot image used to create "El Torito" bootable CDs is a 'no emulation' image. The system will load and execute this image without performing any disk emulation

• boot-load-size: Specifies the number of "virtual" (512-byte) sectors to load in no-emulation mode. The default is to load the entire boot file. Some BIOSes may have problems if this is not a multiple of 4.

• boot-info-table: Specifies that a 56-byte table with information of the CD-ROM layout will be patched in at offset 8 in the boot file. If this option is given, the boot file is modified in the source filesystem, so make sure to make a copy if this file cannot be easily regenerated! See the EL TORITO BOOT INFO TABLE section for a description of this table.

For more information, see man mkisofs.