[syslinux] Nested PXELINUX configurations

[Gene Cumm]

On Thu, Mar 24, 2011 at 18:38, Giannis Roussos
<morpheus at csl.mech.ntua.gr> wrote:
> I discovered di-netboot-assistant , which worked as advertised. The .cfg
> files it produced all have absolute paths without ::.

In PXELINUX, the only paths that are absolute contain a "::" (either
as the first two character or as a separator between an IPv4 address
at the beginning and the path) or are a URL.

The only caveat with my solution is that you may end up with a path
that contains "//" (one from the prefix, one from the path specified
in the config).

> On 24/3/2011 9:27 μμ, Gene Cumm wrote:
>>
>> On Thu, Mar 24, 2011 at 12:59, Giannis Roussos
>> <morpheus at csl.mech.ntua.gr>  wrote:
>>>
>>> Hello all,
>>
>> Comments inline; solution near the bottom.
>>
>>> I have a boot server (running Debian Lenny x64) with a number of bootable
>>> options already configured (freedos, memtest, sysresccd etc).
>>>
>>> What I am struggling to do now is add Ubuntu and Debian netinst images so
>>> that I can boot from the network and have all the boot options available
>>> as
>>> if I was using a CD-ROM.
>>>
>>> The problem is that (as far as I can tell) the Ubuntu and Debian PXELINUX
>>> assume that they are located in the tftp root folder. Since however
>>> Debian
>>> and Ubuntu use a similar file structure, I cant have both distros a the
>>> same
>>> time in the tftp root. (Not to mention the mess this would create in the
>>> tftp root).
>>
>> The structure of the configs is an issue for everything but PXELINUX.
>> PXELINUX actually uses "::" as the character to indicate a root
>> directory.
>>
>>> Idealy I would like to place each distro in a separate folder inside tftp
>>> root (see below) and "chainload" each pxelinux configuration from the
>>> default config file.
>>>
>>> TFTP_root---pxelinux.cfg--->default
>>>    |
>>>    |-------debian------pxelinux.cfg----->default
>>>    |
>>>    |-------ubuntu------pxelinux.cfg----->default
>>>
>>> Since PXELINUX uses (AFAIK) absolute paths, there are two ways to achieve
>>
>> It never uses absolute paths as I mentioned in the post you linked below.
>>
>>> something like this:
>>> 1) Edit all configuration files and add the correct path in all include
>>> arguments. I have done it for Ubuntu and it works but is not practical at
>>> all, requiring a lot of work for each new release.
>>> 2) Find the correct kernel, initrd etc settings for the Ubuntu/Debian
>>> options and add them to the main PXELinux config or a submenu. Again,
>>> this
>>> requires a lot of work to add all the options and the graphics/help of
>>> each
>>> distro wouldn't be available.
>>>
>>> None of the above options is nice and practical, nor allows me to easily
>>> update to newer releases without a lot of work.
>>> Thus, I was wondering if there is some way to chainload the COMPLETE
>>> PXELINUX config of each distro from separate folders. Maybe some option
>>> to
>>> "chroot" pxelinux so that all files are automaticaly loaded from the
>>> nested
>>> folder?
>>>
>>> I have tried copying pxelinux.0 in each of the distros' folders and load
>>> this as a new kernel, but the pxelinux cfg in the tftp root is loaded
>>> still.
>>> Directly loading the main cfg file does not work either since all the
>>> included files are not in the tftp root.
>>
>> Don't use it as a kernel.  Try the following:
>>
>> LABEL debian
>>   COMBOOT pxechain.com
>>   APPEND ::debian/pxelinux.0
>>
>> Please note that if the first PXELINUX is version 4.xx, it must be at
>> least version 4.04-pre1 as there is a bug that was resolved in
>> 4.04-pre1.  I believe 4.04-pre14 is OK but I can't be certain at this
>> time.  For a production environment, I'd advise waiting for 4.04.
>> Otherwise, try 3.86 for now.
>>
>>> The same question has been asked here
>>> http://web.archiveorange.com/archive/v/mwjwmJ0CIqkvn1V88yus but no
>>> complete
>>> answer has been given.
>>>
>>> Thanks for all the help,
>>> Giannis
>>
>> I thought that it was.  I also think that the above post is a little
>> different.
>>
>
>
> --
> -
> ------------------------------------------------------------------------------
>  Giannis P. Roussos
>  PhD Student
>  Control Systems Lab, Mechanical Eng. Dept.
>  National Technical University of Athens
>  9 Heroon Polytechniou Str., Zografou
>  Athens 15700, Greece
>
>  Tel : ++30-210-772-1726
>  e-mail : jrous at mail.ntua.gr
> ------------------------------------------------------------------------------
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-- 
-Gene

"No one ever says, 'I can't read that ASCII(plain text) e-mail you sent me.'"