I've always had /boot on the OS partition but thinking of mounting ESP at /boot to use EFISTUB and boot directly into the kernel from UEFI. The ESP would be using FAT32 (obviously). vmlinuz-linux, microcode, intrd and it's fallback would be on that FAT32 partition.

Would there be any sort of performance impact simply because the kernel is on a FAT32 file system and not on something like EXT4/BTRFS/etc.? Or a slower boot time (since the initrd, microcode is on there)? Is it bad for encrypting a disk (where ESP is unencrypted, and OS partition is encrypted)? What are some other disadvantages of the ESP on /boot? I'm not dual booting with another OS, so that should be fine.


The only disadvantage of using EFISTUB is problem mitigation, I mean, if something goes wrong, you'll rely on booting via USB or something similar.

No perform impact at all, only boot time (if you want to boot faster, but this can be achieved with other bootloaders as well).

The ESP being FAT32 is an UEFI design, doesn't imply a direct security issue since you still need the password to unlock your encrypted partition (unless someone use another kernel/initrd to install a trojan after you type your password). I don't like FAT32 at all, for a filesystem level assurance, you can mount with sync at boot. And yes, you can use ESP as /boot without any further problem.

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