some question on root filesystems

some question on root filesystems

[Julien Eyries]

hello,

here is my situation : i first intented to use NFS as the root
filesystem for our embedded MPC8260 linux but they may be some
hardware design error which stop us to use the intel LXT971A
ethernet controller we have on our custom board.

therefore, i have removed all the network interface in our kernel, and i
try now to use the flash memory (4MB) we have. my question is : what
kind of filesystem is typically used in this case : initrd, cramfs, romfs ?

it seems to me that initrd is a little bit different in the way the
kernel boot over it than the other fs (using /linuxrc , pivot_root and
so on ...), why ?

and for the cramfs and romfs filesystem, how does the sytem "guess" the
memory range where your filesystem lives in ?

can you give me some feedback on the choice you may have made ??

Greetings,


Julien Eyries.



--
Julien Eyries
R&D engineer
Thales Broadcast & Multimedia (ex-thomcast)
email: julien.eyries@thales-bm.com
fax: 33(0) 1 34 90 31 10
tel: 33(0) 1 34 90 31 01

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Re: some question on root filesystems

[Wolfgang Denk]

In message <3CA31782.8020301@thales-bm.com> you wrote:
>
> here is my situation : i first intented to use NFS as the root
> filesystem for our embedded MPC8260 linux but they may be some
> hardware design error which stop us to use the intel LXT971A
> ethernet controller we have on our custom board.

How about fixing the problem? Network is something  which  is  REALLY
nice to have...

> therefore, i have removed all the network interface in our kernel, and i
> try now to use the flash memory (4MB) we have. my question is : what
> kind of filesystem is typically used in this case : initrd, cramfs, romfs ?

Yeas, any of these. And/or MTD + JFFS/JFFS2...

> it seems to me that initrd is a little bit different in the way the
> kernel boot over it than the other fs (using /linuxrc , pivot_root and
> so on ...), why ?

Forget about /linuxrc or pivot_root; these are not  needed  for  what
you are going to do.

See our "Simple Embedded Linux Framework" at
ftp://ftp.denx.de/pub/LinuxPPC/usr/src/SELF/ for a start

> and for the cramfs and romfs filesystem, how does the sytem "guess" the
> memory range where your filesystem lives in ?

It doesn't guess, you have to tell it.

> can you give me some feedback on the choice you may have made ??

The choice depends on the project requirements.

A compressed initrd image is a frequently  used  solution  that  fits
many needs; in some cases cramfs may be more appropriate; if you need
a writable filesystem (for persistent storage of some data) MTD+JFFS2
is quite useful...

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
A meeting is an event at which the minutes are kept and the hours are
lost.

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