[syslinux] Append boot device to /proc/cmdline

Shao Miller Shao.Miller at yrdsb.edu.on.ca
Wed Dec 2 15:39:50 PST 2009

H. Peter Anvin wrote:
> Actually, a lot of people object to it, and so it will not be done
> unconditionally.

For example, there're more than just the Linux kernel that conform to H. 
Peter's i386 Linux boot protocol [1].  Other such items might not 
appreciate the extra information you've suggested that Syslinux provide 
automatically, Patrick.

> Well, it really isn't a trivial question to answer even with help from
> the bootloader, as the BIOS view of things and the Linux view of things
> can be dramatically different.

For example, the checks you suggested, Patrick, regarding HDD size or 
filesystem type seem rather arbitrary.  For Syslinux to implement this 
unconditionally would mean that it would be expected to support this 
forever more.  Even passing a BIOS drive number such as 0x00, 0x80, 
0x81, 0xA0, 0xE0 does not help since it is not a guaranteed one-to-one 
mapping to Linux devices.  There might even come a time when such 
information is not relevant because there is some other, more efficient 
means of notifying the OS of the correct boot media.  An example would 
be the iSCSI iBFT.  Who knows?  Perhaps ACPI tables will be the future 
preferred method for this kind of thing.  To suggest appending the 
filesystem type or the HDD size to /proc/cmdline, I wonder if you 
attempt to rally all Linux distributions towards that cause and check 
the response, what it will be like.

That's not at all to say that a particular COM32 module or some special 
option could not benefit your particular needs, Patrick.  Parted Magic 
is nice.

[1] linux/Documentation/i386/boot.txt

- Shao Miller

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