[syslinux] pxelinux - loading vmlinuz and initrd.gz

Josef Siemes jsiemes at web.de
Mon Aug 11 07:00:17 PDT 2003


Hi,

Paul Schulz <paul at mawsonlakes.org> schrieb am 10.08.03 06:02:00:
> 
> Greetings,
> 
> Hopefully a quick question.. I have been experimenting with 
> pxelinux and have noticed the following, when using initrd.gz
> 
> - vmlinuz needs to exist 'tftpboot' directory,
>   else I get an error from pxelinux.
>   eg. kernel/vmlinuz

It doesn't need to exist. Depending on your configuration it's called 'vmlinuz',
'bzImage', 'kernel' or else. BTW: Why didn't you qoute your config file?

> - vmlinux also needs to exist in initrd.gz 
>   (in the same relative path eg. kernel/vmlinuz)
>   else Linux is not booted.
> 
> [I haven't confirmed which one actually is booted,
> other then the file needs to exist in both locations.]

Usually you put all files in the same directory where pxelinux.0 resides.
This would be the kernel and the initrd. Don't use directories.

> I suspect that vmlinuz only needs to be in 'initrd.gz', 
> and that the pxelinux check can/could be disabled.
> Is this correct?

This last statement makes me wonder if we're talking about the same thing.
What do you mean with that? There's some minimum root filesystem in
the initrd (Initial Ram Disk, Initial Root disk, one of these it's called), the kernel
is completely different from this.

BTW, to answer the different question in this thread: 
pxelinux loads the kernel and the initrd via tftp, and spreads them over the 
memory (especially the kernel is put in at least two different places in memory):
The (real-mode, 16 bit) setup part, which handles first memory setup, this is put
into low memory (<1MB), and the 32 bit part, which is put into high memory
(>1MB). The initrd is put after the 32 bit kernel part, also in high memory. Everything 
is uncompressed by the kernel itself, pxelinux only tells the 16 bit part where to 
find everything, passes the command line etc.pp.

Regards,

Josef

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