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Old 11-23-2006, 02:30 AM   #1
veeruk101
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Booting from PXE


When booting diskless clients, PXE is the way to do it. However, I read up on it and realized that it has to do with installing Linux on the client machines rather than simply booting from it...is my interpretation correct, or can PXE be used to just boot from the installation on the server? It looks like it's got to do with installation because it's talking about kickstart files and other things like that.

Also, for diskless clients, once the OS is loaded from the server, is it just stored in memory or what?
 
Old 11-23-2006, 02:44 AM   #2
paulsm4
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Hi -

Yes, your interpretation is correct.

And yes, once the OS is loaded from the server it can indeed be stored entirely in memory (in fact, this is how "setup" CDs typically work. Including MS Windows "setup") (of course, assuming you've got enough memory ;-)).

And (to a question you didn't ask), you can easily mount and use any peripherals (including hard disks, USB drives and/or network shares) once Linux is running.

Book recommendation:
"Building Embedded Systems in Linux", O'Reilly
http://www.bookpool.com/sm/059600222X
<= There's a whole chapter on network boot options...

Here are a couple of links that might be of interest:
http://tldp.org/HOWTO/Network-boot-HOWTO/
http://www.faqs.org/docs/Linux-HOWTO...ess-HOWTO.html
http://frank.harvard.edu/~coldwell/diskless/

'Hope that helps .. PSM
 
Old 11-23-2006, 03:02 AM   #3
odcheck
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PXE is used to boot directly from a nic.
TFTP is the server that holds informations and the boot image file for the client that tries its boot attempt.
DHCP is also needed.
 
Old 11-23-2006, 04:07 PM   #4
paulsm4
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Hi, again -

Your original post was correct. Odcheck is also correct.

The fact is that accomplishing a "diskless boot" involves SEVERAL steps, SEVERAL protocols and will probably involve several DIFFERENT software components. There are different choices you can make at every step.

Nevertheless, it ISN'T rocket science - it can actually be pretty straightforward and simple.

Take a look at the links I posted, veeruk101, and see if any of the information looks appropriate for your situation. Please post back if you have any questions.

Good luck .. PSM
 
Old 11-23-2006, 09:12 PM   #5
veeruk101
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Thanks for your responses.

Reading up on this, I've become confused by what PXELINUX actually is...it's being described as a boot loader. Things like LILO and GRUB are also boot loaders, right? So are these alternatives to each other, except that PXELINUX has some other functionality? Does the boot ROM choose between LILO, GRUB, and PXELINUX? How?

Also, I've tried looking up about the purpose of initrd, but can't understand what they're saying. On a diskless client, would you download a kernel to RAM, then create an initial ramdisk, then get rid of it and start up another one? Could somebody please explain this concept in clear, simple (beginner) terms?

Thanks.
 
Old 11-23-2006, 10:53 PM   #6
Sepero
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No, PXE is not the same as GRUB or LILO. GRUB and LILO (bootloaders) define what system will be booted. PXE is a system that gets booted. (MS has it's own bootloader)

initrd is used on many Linux systems in case of disaster. The kernel boots with the "initrd" as a sort of pre-root system. If the real root system is bad, then there are minimal programs on the "initrd" for saving/correcting the real root.

"initrd" is optional and may or may not be used with any given Linux system, depending on how it was created.
 
  


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