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rasheed

Boot block padding

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When I use isolinux to create multi-boot cd with ImgBurn I get a following error:

There is a problem with the El Toritio configuration!

 

Boot Image File blah\blah\blah\isolinux.bin

size: 12 331 bytes

 

The file size is not a multiple of 512.

mkisofs doesen't seem to care about this, as it builds the bootable image without any errors.

 

If I manually pad the boot image file (isolinux.bin) with zeroes, ImgBurn accepts it, and the resulting cd boots without trouble.

 

What I am politely asking is would it be much of a trouble to add following options to ImgBurn:

 

1. To ignore the size of the boot loader (mkisofs behaviour)

 

and / or

 

2. To automatically pad the boot loader with zeroes until it fits the "multiple of 512 bytes" rule.

 

Personally, I would prefer the first option (if possible) , since padding the boot image with zeroes may cause problems with boot loaders that have checksum protection.

 

 

Thank you in advance.

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This is more of a sanity check than anything and very easy to get rid of.

 

As El Torito works in sectors, the last one will always be padded with zeroes if it's not quite 512 bytes - there's no way around that. Beyond that, the Mode 1 CD/DVD is obviously 2048 bytes so that 512 is potentially padded by an extra 1536 zeroed bytes - but they won't be referenced in the 'Sectors to load' bit.

 

What I don't understand is why that isolinux program doesn't just output it so it's a multiple of the sector size. I can't think where it could be used where 512 byte sector sizes DON'T come into it, so why not make it a multiple of 512 in the first place?

 

I wouldn't dream of outputting an ISO that wasn't a multiple of 2048 or whatever.

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