RE: Can I run Linux without a file system?

RE: Can I run Linux without a file system?

[Hihn Jason]

There are people here who can help you more than I, but I'll take a gander.
This is what I believe to be correct:
Yes. You will always have SOME kind of filesystem. But this begs another
question. How much do you know about Linux, and what are you really asking?
The /proc filesystem is not really on any disk, just like /dev (I think)
isn't on any disk, though they look like to us users that they are
filesystems.

If you want to run a program, where will it come from? There are filesystems
made for RAM, like cramfs or ramdisks, or flash filesystems complete with
wear-leveling. Maybe you can just jump to an offset and start executing code
if all you have is just a kernel and a program. If that is the case then
maybe you'll have to call your program 'init' or change the source of the
kernel to invoke your program.

Does this help?

I reserve the right to be wrong.


-----Original Message-----
From: Tim Lai [mailto:laitingwai@yahoo.com]
Sent: Friday, June 21, 2002 11:09 AM
To: linuxppc-embedded@lists.linuxppc.org
Subject: Can I run linux without a file system?



I am porting linux on a custom board.
I am using the bootrom to load vmlinux onto
RAM, and I am in the middle of getting the console/
serial driver to work.
All the documents I read have refer the console as
/dev/ttyS, and state that to communicate to the
console, I have to set it up with open("/dev/ttyS").

Does that means I have to have some sort of file
system in linux?

Thanks.


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RE: Can I run Linux without a file system?

[Tim Lai]

Thanks, Jason.
I am new to linux kernel. I'll have the main
application run from init(), so I wasn't planning
to have a file system.

> Yes. You will always have SOME kind of filesystem.
> But this begs another
> question. How much do you know about Linux, and what
> are you really asking?

If /proc and /dev is not really on any disk, what do
I have to do to init or create /dev? Do I need ramdisk
as a minumum requirement for linux?
My main goal right now is to get the serial port
to work, so I can do some debugging with the dumb
terminal. After I do tty_register() in the serial
driver, does linux assign /dev/ttyS to this device?

> The /proc filesystem is not really on any disk, just
> like /dev (I think)
> isn't on any disk, though they look like to us users
> that they are
> filesystems.
>

Can you give me pointers on which file to read?

>
> Does this help?
>

Yes. Thank you very much. :)


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Re[2]: Can I run Linux without a file system?

[Ricardo Scop]

Tim,

Maybe initrd and linuxrc is enough for your system. Read the file
initrd.txt in the Linux source tree Documentation sub-directory.

[]'s, Scop                            mailto:scop@vanet.com.br

------------------------------------------------------------------
It might look like I'm doing nothing, but at the cellular level I'm
really quite busy.

Friday, June 21, 2002, 4:35:17 PM, you wrote:


TL> Thanks, Jason.
TL> I am new to linux kernel. I'll have the main
TL> application run from init(), so I wasn't planning
TL> to have a file system.

>> Yes. You will always have SOME kind of filesystem.
>> But this begs another
>> question. How much do you know about Linux, and what
>> are you really asking?

TL> If /proc and /dev is not really on any disk, what do
TL> I have to do to init or create /dev? Do I need ramdisk
TL> as a minumum requirement for linux?
TL> My main goal right now is to get the serial port
TL> to work, so I can do some debugging with the dumb
TL> terminal. After I do tty_register() in the serial
TL> driver, does linux assign /dev/ttyS to this device?

>> The /proc filesystem is not really on any disk, just
>> like /dev (I think)
>> isn't on any disk, though they look like to us users
>> that they are
>> filesystems.
>>

TL> Can you give me pointers on which file to read?

>>
>> Does this help?
>>

TL> Yes. Thank you very much. :)

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Re: Can I run Linux without a file system?

[Dan Malek]

Tim Lai wrote:

> I am new to linux kernel. I'll have the main
> application run from init(), so I wasn't planning
> to have a file system.

So, why are you trying to use Linux?  If you don't start
up applications outside of the kernel, there aren't very
many features that make it attractive or useful.


	-- Dan


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Re[2]: Can I run linux without a file system?

[Ricardo Scop]

Tim,

See bellow...

[]'s, Scop                            mailto:scop@vanet.com.br

------------------------------------------------------------------
It might look like I'm doing nothing, but at the cellular level I'm
really quite busy.

Friday, June 21, 2002, 4:42:34 PM, you wrote:


TL> I am interested in both input/output operation
TL> on the console. If I just set CONFIG_SERIAL_CONSOLE,
TL> will I be able read input from the console?
TL> The main application will be started from init(),
TL> and the application will need to read and write
TL> to the console. Are there are method to communicate
TL> to the serial port other than open("/dev/ttyS0")?
Not AFAIK. The VFS (Virtual File System) is at the very heart of Linux
and _is_ the abstraction used to deal with I/O devices. You don't need
to try avoiding it. A simple initrd will do the job and can be as
light as you make it.

>>
>> You don't need a filesystem to get output on the
>> serial console
>> you just need to enable the console with
>> CONFIG_SERIAL_CONSOLE=y
>> in your kernel configuration (atleast for mpc860
>> that all)
>> but you will have a hard time producing much more
>> than a blinking
>> cursor if you boot a Linux kernel and have no
>> application that
>> it then can run on the root-filesystem - what would
>> be the point
>> of such a setup - 1MB kernel code for a blinking
>> cursor on a
>> serial port seems expensive.
you get the network protocol stacks, too...

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Re: Can I run Linux without a file system?

[Tim Lai]

Well, there is memory protection for now.
And when new hardware arrives, we'll have
file system.

--- Dan Malek <dan@embeddededge.com> wrote:
>
> Tim Lai wrote:
>
> > I am new to linux kernel. I'll have the main
> > application run from init(), so I wasn't planning
> > to have a file system.
>
> So, why are you trying to use Linux?  If you don't
> start
> up applications outside of the kernel, there aren't
> very
> many features that make it attractive or useful.
>
>
> 	-- Dan
>
>
>


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