Re: failsafe booting..

[Jochen Hoenicke]

On Oct 5, Alessandro Rubini wrote:
> 
> I didn't look at filesystem code in grub, but I don't think it should
> be too difficult to implement "mv". The only issue I see is that
> currently FS access is read-only, while in this case you require write
> access, and this can introduced non-trivial issues when you deal with it.

mv is non trivial if the length of the file names differ.  If the new
file name is longer this can even lead to allocation of new blocks.
For FAT with long filenames it can be even complicated if the length
doesn't change.

All you need is to remember the default entry at a position where grub
can change it.  See the thread "default is static" some time ago:

http://www.mail-archive.com/cgi-bin/htsearch?config=bug-grub_gnu_org&words=default+is+static

It is possible to reserve a word somewhere in start.S (the first
sector of stage1_5 / stage2) for this purpose.  Since the boot sector
contains its block number and start.S should be still resident in
memory, it should be quite trivial to replace the word.

  Jochen