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Re: Using grub, is it possible to use "if, while" during booting (before

From: Binh Minh
Subject: Re: Using grub, is it possible to use "if, while" during booting (before loading normal.mod)?
Date: Tue, 13 Aug 2013 07:33:28 -0700

It is a security feature requires my implementation to ask for the user's input and compare the input before we process information in grub.cfg.  It is proprietary so I can't discuss more than that.  If I include modules echo, sleep, read during grub-mkimage, I was able to have those commands in myconfig.cfg, and this works before normal.mod is loaded.  But how come "if" statement is unknown?  The grub documentation on this web site has an example showing using "if" statement is possible.  What kind of built-in script parser is used when processing the "config file" that was linked into core.img?

On Tue, Aug 13, 2013 at 2:39 AM, Andrey Borzenkov <address@hidden> wrote:
On Tue, Aug 13, 2013 at 9:10 AM, Binh Minh <address@hidden> wrote:
> I am trying to read in a user's input, compare the user's input to X.  If
> the user's input matches X, proceed to load normal.mod; otherwise loop back
> to get user's input.

And why you cannot do it after normal.mod is loaded?

> On Mon, Aug 12, 2013 at 7:39 PM, Andrey Borzenkov <address@hidden>
> wrote:
>> В Mon, 12 Aug 2013 13:39:24 -0700
>> Binh Minh <address@hidden> пишет:
>> > My computer has grub installed. During booting before normal.mod is
>> > loaded,
>> > I need to be able to run if and while commands in my config file which
>> > has
>> > been linked into core.img (using grub-mkimage -c myconfig.confg). In
>> > myconfig.config, I have an if statement and I kept getting "unknown
>> > command
>> > if" during booting.  I saw an example in
>> >
>> >
>> > looks like I just need to include search, test, and normal modules.
>> > Am
>> > I missing something?  Thanks
>> It is not possible. Those commands are provide by normal.mod. The only
>> purpose of core.img is normally to load normal.mod.
>> What are you trying to do?

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