On Mon, Dec 14, 2009 at 8:18 AM, Zhu Yi <yi....@intel.com> wrote: > On Fri, 2009-12-11 at 17:39 +0800, Felix Zielcke wrote: > > > > Someone already made a patch for this inside grub-setup > > See here and also for the discussion of it: > > http://lists.gnu.org/archive/html/grub-devel/2009-09/msg00242.html > > Thanks. If I knew this patch, I won't try to write one my own. I did do > some basic search and asked in #grub2 IRC before writing it though. > > Anyway, I did a quick review for Garimella's patch. Both the ideas of > the two patches are the same: backup the mbr and boot sectors will be > overwritten by core.img to a file before grub2 overwrites them. The > implementations slightly differ in: > > 1. The format of the backup file. > > The old boot sectors and the start of embed_region position is required > for both patches. Garimella also added some redundant fields (i.e. image > size and 0xff) for integrity checking. I think it's a good idea. But > something like a md5/sha1 checksum should be even better. > > 2. The image backup and recovery. > > Both of the patches choose to backup the old boot sectors in > grub-setup.c. On the recovery, Garimella selected to do it in > grub-setup.c and I used grub-install script with dd(1). I don't think > this is a very big deal and either way is OK. The reason I choose > grub-install is I want to keep the grub-setup.c as clean as possible. > Because given the backup file format, one can recover it with dd(1) even > without any help with grub-setup. > > md5/sha sum is a good idea. If you want, I can implement it.
> 3. The backup policy. > > Garimella's patch backups every time before grub-setup overwrote the > boot sectors. There might be a problem when someone run > grub-setup/grub-install twice. So the backup image ends up with the > grub2 boot sectors. This makes the recovery for the "real" boot sectors > impossible. My patch won't overwrite if a previous backup image already > existed. grub-install will remove the backup image after a successful > recovery. > I think this is questionable. Some prefer to backup only the previous copy of mbr. Some prefer to save the oldest copy. We can take the users' opinion. > 4. Blocklists installation. > > This is not very important because blocklists is not recommended. To be > completeness, my patch backups the mbr if blocklists are used due to > embedding is not possible. This will be detected by grub-install as > well. > > > In conclusion, I believe this backup feature is useful and either > implementation should do the work. If we can merge the good parts of > them, we can get a better one. I just curious why the thread is stuck > since September. Any blocking issues with it? Can we keep the topic > moving forward? Your comments are highly welcome. > > The reason is very simple. If you are good user, you should have already backed up your copy on your own. And this feature is not necessary. -Garimella Kashyap
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