[syslinux] Structure of VBR in FAT32?

Avi Deitcher avi at deitcher.net
Tue Jan 2 23:25:49 PST 2018

Sorry for the late response. I am set to digest on this list. One of my
chief complaints about mailman (besides non-searchable archives), is that
you can either get every message or digest, but not "digest except for
threads to which I have responded for which I want every message directly".

>  The command line installers have the core module and the bootloader file,
all embedded

Makes sense.

> If you don't have the ldlinux.sys file in your system, it would mean
> that you only have "binary" packages of SYSLINUX and/or EXTLINUX (and
> the bootloader has not been yet installed).

Bingo. I downloaded the actual upstream official archives, as you
suggested, looked under bios/core, it all is there.

> FWIW, the VBR in FAT32 doesn't have to be 512 bytes; FAT32 has the
> possibility to use more than one sector for boot purposes. In fact,
> Microsoft's FAT32 VBR uses at least 3 sectors (IIRC, typically, 32
> sectors)

I did not know that. I just finished writing a go-lang library
implementation of fat32 (mainly to manipulate image files), I missed that.
How do you tell if it is the "usual" single sector of 512 bytes or more?
Wouldn't there need to be some flag at some location? Or is the assumption
that fat32 can skip any number of sectors until it reaches one with the
magic signature 0x55AA and it takes all sectors from 0 until that one as
the VBR?

> moving ldlinux.sys within a FAT32 boot volume could
> potentially affect the boot process when using SYSLINUX. In such case,
> executing the command line installer would be the simplest/quickest
> solution.

But even so, it installs the first 512 bytes in the VBR, then those bytes
need to find the next bytes (ldlinux.sys). Even if I use the installer, and
then move the files, unless the actual blocks remain the same, it will be
lost, right?

Avi Deitcher
avi at deitcher.net
Follow me http://twitter.com/avideitcher
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