Re: --recheck option

[Jordan Uggla]

On Thu, Jul 5, 2012 at 5:19 AM, address@hidden
<address@hidden> wrote:
> Dear GRUB devs/helpers,
>
> A) Which are the situations where the --recheck option of grub-install must
> NOT be used? why grub-install wouldn't systematically probe a device map by
> default?

With grub 2.00, it does.
http://www.gnu.org/software/grub/manual/grub.html#Device-map .

>
> B) Some people recommend to use "grub-install /dev/sdX && grub-install
> --recheck /dev/sdX", do you think it is correct/useful?

As explained in the above documentation, grub utilities no longer need
a device.map file. Back when they did still need one, the first time
someone ran grub-install it would write a device.map (if one didn't
already exist). If that got out sync somehow then a later grub-install
might fail, and if that happened using the --recheck option (which
would write a new device.map, overwriting the old one) might allow the
installation to succeed.

Now, grub-install probes on the fly if no device.map exists, and never
creates a device.map file itself, and so "grub-install --recheck ..."
now actually simply deletes the device.map file, causing grub-install
to go back to the default state of probing on the fly.

Running grub-install twice is redundant, and adding the '--recheck' is
also usually not needed option at this point but won't hurt anything
(except in very specific situations like when you're passing an LVM
logical volume to a virtual machine as if it were a normal disk, in
which case you should know what you're doing and have a backup of your
device.map anyway).

So the advice is a little silly at this point, but not harmful.

-- 
Jordan Uggla (Jordan_U on irc.freenode.net)