On Wed, Nov 26, 2025 at 5:15 PM Daniel Gerber <[email protected]> wrote: > > Hi, > > Is there a way to install grub to the VBR of an exfat-formatted > partition? > > > grub-bios-setup: error: hostdisk//dev/sdb appears to contain a exfat > > filesystem which isn't known to reserve space for DOS-style boot. > > Installing GRUB there could result in FILESYSTEM DESTRUCTION if valuable > > data is overwritten by grub-setup (--skip-fs-probe disables this check, > > use at your own risk). > > ExFAT reserves 390 octets (<420o in FAT32) at offset 0x078, plus the > whole second sector, for boot code. > <https://wiki.osdev.org/ExFAT#Boot_Sector_Structure> > Am I correct that grub could put its boot image there and it's just not > implemented? >
Yes, you are. > For context: the goal was to devise a single device structure bootable > "everywhere" (MBR or UEFI, different platforms), with the simplest > possible partitioning (1 part) and accepting iso files >4Go, on a very > widely supported filesystem. Blocklist install is always an option. > Hence the idea of just one big "ESP" formatted with exFAT. But then > there are further issues: > - Most UEFI firmwares out there only support FAT32, not exFAT, right? Right. > - "Apple machines (like iMac and MacBooks) only accept HFS+ FS on the > ESP." <https://wiki.osdev.org/EFI_System_Partition> Maybe tacking a > second, HFS+-formatted, ESP would convince those machines to boot from the > same device? > > > Thanks in advance for your comments, > Daniel > -- >
