[U-Boot-Users] jffs2

[Wolfgang Denk]

In message <20030306084614.GA16290 at pengutronix.de> you wrote:
>
> I have the impression that we don't really understand each other :-) 

Maybe I should give up and let you stay frustrated about JFFS2 ;-)

> You download an image, containing a kernel, a root fs which must be
> writable without having all this in a filesystem? How do you do this? I

I don't do it this way. Usually I split  filesystem  and  kernel,  as
this gives both more flexibility and easier to handle image sizes.

I then write  the  kernel  image  to  one  raw  partititon,  and  the
filesystem image to another raw partition.

> mean, it's clear that you simply download one _image_ file of the fs
> which you write to /dev/mtd/*, but what's _inside_ the image? For a raw

What is in it? I guess, what you put in?  Sorr,  I  don't  understand
your problem.

> kernel without rootfs it's clear that you can write it to a partition
> and be ready. But with rootfs? Being writable? Please excuse me, but I
> seem to be too stupid to understand your.   

It is IMHO a bad idea to have the root  filesystem  writable  in  the
first  place.  Usually  it  means that you don't understand (probably
never bothered about it) what's going on in your filesystem. You  may
end  up  easily  with  a  system that fails in the field after just a
couple of weeks / months because  of  unintended  and  unknown  write
operations.

I always propose a design with a  read-only  root  filesystem,  which
contains   all   the  "constant"  data  like  libraries,  tools,  and
applications, and only a small writable  flash  filesystem  (if  any,
often it makes no sense at all) for things like configuration data.

But here it goes: if you do it this way - what do you need JFFS2 for?
For logfiles? Bad choice. For config data? You can probably  use  the
U-Boot  envrionment  sectors  as  well - now that we have implemented
redundancy this is a pretty safe method  for  anything  that  can  be
represented as (short) string.

> And what is DPLG? 

You do read this list, don't you?

See http://www.denx.de/re/DPLG.html


Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
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