Upgrading cramfs root file system while running (DENX wrote that is not possible)

[Antonio Di Bacco]

Little bit off topic:
I decided to adopt a different strategy, the sw download web page will contain 
a java applet that will act as a tftp server, then the board will be rebooted 
and an environment variable will instruct the u-boot to tftp the new software 
from the applet. What do you think? I know that applets cannot read local 
files on the PC, unless they have a valid certificate but the user should 
trust me.

Bye,
Antonio.

On Friday 21 April 2006 22:23, Wolfgang Denk wrote:
> In message <200604210853.32860.david.jander at protonic.nl> you wrote:
> > What do you mean with "something bad could happen"?
>
> System crashes.
>
> > The only thing I can think of is pulling the power plug while flash is
> > being erased or written. What else could go wrong?
>
> The kernel may try to (re-) load some pages of a  running  executable
> or  library  which  is  no  longer  available  (at  least  not at the
> addresses where they used to be). The kernel will either stumble over
> what it believes to be a corrupted file system,  or  load  the  wrong
> data -> kaboom.
>
> > We do the following: system running from read-only jffs2 partition.
> > Sometimes that partition is remounted read-write and single files are
> > replaced, but in some occasions we need to upgrade the whole fs. In that
> > case a CGI lodas the image into a ramdisk, and the upgrade process is
> > started. For upgrade,
>
> You *have* to unmount the old file system here.
>
> > partition, and then "dd" again to copy the image. At that point no
> > critical flash-read access should be requested since dd is already in
> > cache (it's
>
> The kernel might reload any page of any running executable or library.
>
> Best regards,
>
> Wolfgang Denk