[syslinux] syslinux versus pxelinux

[Pascal Vandeputte]

Geert Stappers wrote:
> Op 02-05-2007 om 18:25 schreef Pascal Vandeputte:
>> Hello,
>>
>> I've been digging some more during the last couple of days [...]
>>
>> So now I've got a nice ubcd403.img file. If I dd it to a flash drive
>> in /dev/sda I can perfectly boot the "Ultimate Boot CD" from it.
>>
>> So I tend to think the disk image file itself is okay.
>>
>> However, making it available through pxelinux as follows doesn't work:
>>
>>     label ubcd
>>         kernel memdisk
>>         append initrd=images/test/ubcd403.img harddisk
>>
>> The machine just hangs there at "Loading boot sector... booting..."
>>
>>
>> What am I doing wrong?
> 
>   :-)
> 
> 
> Several things, one is asking "What am I doing wrong?"
> 
> <preach>
>    Make the challenge a common challenge by avoiding 'I'.
> 
>    Wrong is the wrong word, there is nothing wrong with a expriment.
>    If an expriment does learn you something, it is good expriment.
> </preach> 
> 
> 
> The missing knowlegde ( in fact the missing imagination ) :
> 
>  Syslinux is started from ROM and loads a kernel or program from floppy
>  or other FAT filesystem and starts it.
> 
>  Isolinux is started from ROM and loads a kernel or program from CD
>  and starts it.
> 
>  PXElinux is started from ROM and loads a kernel or program from the
>  network and starts it.
> 
> 
> 
> What your expriment proves, is that you have started PXElinux starting
> a syslinux that can't do it's job.


Well, to make a long story short:
  - my first attempts were to do it similar to what worked with FreeBSD: 
dd + fdisk + mkdosfs etc, but this was leading nowhere.
  - before mailing to the list I upgraded from 3.07 to 3.36 which 
actually made matters worse (see other mails in this thread).
  - then I started using mkdiskimage which was effectively the correct 
way to do it, but because of the bug in 3.36 it still wouldn't work.
  - last but not least, the "syslinux" package in Debian Sarge was no 
good either (still 2.11, "can't find linux image").



So let's summarize a few pitfalls to avoid when converting 
ISOLINUX-based ISO images/cd-roms to disk images for PXE booting:

  - Use the "mkdiskimage" script (from the syslinux package) to create
    an empty disk image.
    Do NOT try to do the same thing with dd + fdisk + mkdosfs/vfat,
    it will not work easily because of the boot code in the MBR.

  - Never use the syslinux package which is available through the
    package management of your GNU/Linux distribution, as it is bound
    to be outdated (e.g. the 2.11 in Debian Sarge was no good match
    for UBCD403).

  - Don't use atftpd for serving files, but use tftpd-hpa instead.
    atftpd bails out when files get larger than 90MB, which is not much
    these days.
    Even if you think you're using tftpd-hpa, double-check it anyway,
    you never know if someone changed a few things without informing
    you. :/

  - Don't assume that newer SYSLINUX releases are always better. If
    you're following a howto and it won't work, try to use the same
    software versions as the author of the howto. (if available)



Howto coming up...


Greetings,

Pascal Vandeputte