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Re: Chainloading isolinux.bin

From: 4javier
Subject: Re: Chainloading isolinux.bin
Date: Wed, 3 Feb 2016 20:23:37 +0100

In effect I have the El Torito boot catalog in the same directory, and its size is 2KB. But If I open it with an hex editor, it has just early byte wrote, and about 90% of the rest is just filled with zeros. I think it's due to blocksize. But I can't understand how it could be just 2KB when blocksize of the partition is 4096. Shouldn't it be 4 KB?

2016-02-03 15:39 GMT+01:00 Andrei Borzenkov <address@hidden>:
On Wed, Feb 3, 2016 at 5:29 PM, 4javier <address@hidden> wrote:
> You're right. My fault thinking that "chainloader" command would have ran
> directly the chained bootloader with no need of "boot" command. Anyway, I
> just tried, and shell just shows a blinking cursor on a new line, doing
> nothing.

Well ... chainloader command loads single sector. El Torito boot image
can be of arbitrary (withing some limits) length. As soon as
isolinux.bin exceeds 512 bytes, it's going to fail.

Second problem is whether isolinux.bin was built for specific memory
address and for which one (this information is present in El Torito
boot catalog and is missing here of course).

Third consideration is, block size on CD is 2048 bytes which does not
match what you have on HDD (either 512 or 4096). It will likely make
it impossible for isolinux.bin to read anything.

> 2016-02-03 14:51 GMT+01:00 Andrei Borzenkov <address@hidden>:
>> On Wed, Feb 3, 2016 at 3:20 PM, 4javier <address@hidden> wrote:
>> > chainloader /isolinux/isolinux.bin
>> >
>> > I always get Error: Invalid Signature.
>> > If I try to force chainloading, it just get back to the prompt.
>> >
>> Every loader command in grub just "get back to prompt". You need to
>> use "boot" command to actually jump to loaded code (but I doubt it
>> will work).

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