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

[Antonio Di Bacco]

Yes, I also thought this too. Anything important should stay already in RAM 
but there is a chance that something bad could happen. Probably the best 
thing is what you suggested as second option but I have not so much ram. My 
CGI writes the downloaded new software in RAM and then I should directly jump 
to u-boot without leaving Linux the chance to mix things up and then u-boot  
should copy the RAM to the flash. It seems a strange procedure but what else 
could be done with 4MB flash and 16 MB ram? 

Bye,
Antonio.

On Thursday 20 April 2006 22:18, White wrote:
> make it easy: if you start an application which do the flash and after
> this a reset.. nothing should happen. I do it that way.
> the application resist completly in RAM .. and all important libs are
> in RAm or in Filesystem Cache.
> It's only important that you pretend any Application from accessing
> Datafiles or start of new application ...
>
> Alternativly, you can put it in a reserved RAM Area ( mark it not
> usable by Linux) and put a Flash Code in your Bootloader (U-boot?)
> after a reset....
>
> But overwrite a cramfs works for me on >100 times without problems.
>
> Am Thu, 20 Apr 2006 21:54:45 +0200 schrieb Antonio Di Bacco
>
> <antonio.dibacco at aruba.it> :
> > Yes you are right, it is not a good idea to overwrite working cramfs
> > filesystem. But what happens if I download the new cramfs plus kernel in
> > RAM, do a checksum and then, completely in kernel mode, disabling all the
> > interrupts, I write to flash? No process could complain that I am
> > overwriting because no one is executing.
> >
> > Bye,
> > Antonio.
> >
> > On Wednesday 19 April 2006 09:42, Wojciech Kromer wrote:
> > > Dnia 2006-04-06 22:38, Użytkownik Antonio Di Bacco napisał:
> > > > Hi,
> > > >
> > > > how could I upgrade my cramfs rootfs? I have a CGI in the rootfs that
> > > > receives the new rootfs from a web interface and then tries to write
> > > > it in the flash. While overwriting the old cramfs, the CGI will
> > > > continue to work? something weird could happen?
> > >
> > > Generally it's not a good idea to override working filesystem ( I've
> > > tried to do it once).
> > >
> > > You can have two separate copies of filesystem, one to work with, and
> > > another to overwrite, it requires more flash.
> > > Another way is working in initrd, it requires more RAM.
> > > You can also use jffs2 or jffs3 (experimental) to have read-write
> > > filesystem, and change applications only, not whole filesystem (be
> > > carefull with changing busybox or libraries!)
> >
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