[syslinux] Maximum line length of APPEND option in PXELINUX
Jim Cromie
jcromie at divsol.com
Fri Feb 25 06:47:42 PST 2005
H. Peter Anvin wrote:
> Jim Cromie wrote:
> >
>
>> perhaps its worth pointing out that 255 is a kernel limit - unless
>> Documentation/i386/boot.txt
>> is oo-date:
>>
>> **** THE KERNEL COMMAND LINE
>>
>> The kernel command line is a null-terminated string up to 255
>> characters long, plus the final null.
>>
>> so any error msg from pxelinux is reflecting the fact that you wont
>> succeed anyway.
>>
>
> Indeed it is. I seem to remember it being an explicit request on this
> mailing list that it didn't fail silently like it had been.
>
failsafe good. mysterious-fail bad.
> Now, with bootproto 2.02+ it should be possible to extend the limit in
> the kernel. For syslinux 3.xx it should be pretty easy to extend the
> limit in syslinux to match; for previous versions of syslinux it would
> be much harder.
>
> -hpa
>
IIUC, an rdev-like kernel image reading could know the kernel is 2.02+,
and (I infer from this thread) such kernels are able to handle >255
command-lines.
to determine this property, youd fetch the kernel 1st, then look inside it,
and *then* prepare the command-line. OR prepare cmdline before fetch as
if >255 is ok,
and truncate and warn if bootproto <2.02.
in any case, virtually all 2.4.x kernels are 2.02+, and all 2.6.x are.
is that close enough, or did I get all crossed up ?
my $.02 - dont bother doing long-cmdline for 2.xx, its now legacy..
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