Re: [PATCH] Backup old boot sectors before installation

[Zhu Yi]

On Tue, 2009-12-29 at 06:04 +0800, Isaac Dupree wrote:
> > Option 1~3 requires the recover has the knowledge of the backup file
> > format somehow, but a simple dd is enough for option 4. What do you
> > think?
> 
> If the partitioning had been changed in the mean time, 4 would overwrite 
> it with the older values. Similar problem for a weird setup with 
> partitions in between (I dunno, might be possible with GPT or other 
> weirdness).

Good point.

> I think option 2 or 3 is soundest.  Option 2 would have three separate 
> files of information, (right?), and there must be a pretty 
> straightforwards `dd` option to skip to the correct start position. 
> Option 3 would omit the "start position" file... but that file is really 
> cheap, maybe we'd better keep things simple for restorers and stick with 
> three separate files.(Or, we could do something weird like putting 
> start-position somewhere in the filename of the backup.)

This requires the restorer to understand the role of each of the 3 (or
2) files and use `dd' twice with correct options. So an important thing
is, we need to document this somewhere. And I think the best place is to
"document" it in the grub-install script. Because this will enable the
not-so-advanced user to recover her boot sectors easily as well.

If we decide so, we go back to option 1 (my original implementation).
Because the backup file format is not important any more as it is
totally transparent to the restorers. Am I right?

Thanks,
-yi