Message-ID: <67df3057@news.ausics.net>
From: not@telling.you.invalid (Computer Nerd Kev)
Subject: Re: F2FS On USB Sticks?
Newsgroups: comp.os.linux.misc
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Date: 23 Mar 2025 07:49:11 +1000
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The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 22/03/2025 01:42, Computer Nerd Kev wrote:
>> rbowman <bowman@montana.com> wrote:
>>> On Fri, 21 Mar 2025 19:11:40 +0000, The Natural Philosopher wrote:
>>>> My other usage is Raspberry Pi SD cards which are two partitions in IIRC
>>>> VFAT and EXT4
>>>
>>> That may be inherited from Debian.  vfat is used for /boot/firmware or /
>>> boot/efi for UEFI compatibility.
>> 
>> Not from Debian, but for the same reason that like UEFI, the RPi
>> firmware only has drivers for FAT (FAT32, or FAT16 works too,
>> I'm not sure if any new ones support exFAT).
>> 
>> To run in a tmpfs, I set up Linux on a FAT partition on an SD
>> card. No need for a separate EXT* partition if you're not mounting
>> any as / anyway.
>> 
> Then what are you mounting as / ?

The tmpfs.

> I don't understand Linux needs a root filesystem that accepts linux 
> permissions, VFAT does not

Yes, but it can hold a file containing the filesystem data which is
unpacked into RAM during start-up. In fact this is common behaviour
with initrd unpacked to RAM during kernel initialisation and
mounted as /, after which the kernel can set up the partition it
wants to use as / and chroot to that. That second partition can be
an ext4 filesystem such as RPi OS uses, or it can be a tmpfs or
ramdisk with contents unpacked from an archive on the FAT FS into
RAM by the init script in the initrd. Or / can even just stay in
the initrd forever (which is what happens in most distros if the
latter steps fail).

So a Linux file system is really optional. The only FS you _need_
for booting on RPi or UEFI is FAT, because that's what the firmware
can load the Linux kernel from.

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