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Comment by sp1rit | Hacker News Reader

The ESP is just a FAT-32 partition, so its capable of being up to 4GB (by default). At 4GB you can probably store most linux distributions on the ESP, so the title makes it less impressive than it is.

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Technically the ESP doesn't have to be a FAT32 partition. UEFI has file system drivers installable at runtime [1], so you could have an ESP partition that isn't FAT32... assuming that the file system driver for it is loaded. UEFI implementations must have built-in support for FAT per the specification, but you'd need to slipstream any extra EFI drivers into your platform's firmware that are required to get to the ESP.

I think that ESP partitions formatted as HFS+ were a thing on Intel Macs, but I've never had one to try it out.

[1] rEFInd's website lists a bunch of available file system drivers: https://www.rodsbooks.com/refind/drivers.html#selecting

IIRC FAT32 is the only that needs to be supported for a valid UEFI implementation. So to actually have something like that alpine image work for most it does need to be limited to that.

There are also standalone EFI drivers that can be loaded by other means: https://archlinux.org/packages/extra/any/efifs/ (e.g. systemd-boot loads these if they are installed to `<esp>/EFI/systemd/drivers/`)

I guess one could do something like put a large ext4 file image on the FAT32 partition and mount that from within Linux.

Except most ESP partitions I have seen are in the 200MB range.

So now you're asking your users not only to bless the EFI loader, but also to resize their ESP, and most likely system partition.

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