OfflineOS will need to support at least three file systems.

• FAT32 for booting via UEFI
• ISO-9660 for reading CD-ROMs and DVD-ROMs
• Something that supports symbolic links for the installation-proper

Additionally exFAT or NTFS would be desirable for transferring files to Windows as well as some Linux file systems such as journal-less Ext4 or even F2FS.

Since OfflineOS targets UEFI it will also need to support GPT (GUID Partition Table) formatted drives. MBR support is likely to also be needed to mount external flash drives.