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Re: Live softphone USB key.: Progress report

palama@inwind.it wrote:
- Two of these machines have a BIOS which is not capable of booting off a USB key. It is certanly possible to boot on these machines using a boot floppy
It's important to understand that for a computer beeing able to use USB disk, it needs some drivers. Where do they come from ?

a) From modern BIOSes: they support booting of USB disk by supplying a poor-man driver which is only available to the boot-loader and only for the disk used to boot from. This allow boot-loaders to load kernel and initramfs from the USB disk they where booted from, not from another one ! But once control is given to kernel, this driver is no longer available.

b) From linux kernel modules in initramfs.

With a PC BIOS not supporting USB boot, it is worth knowing that most popular boot-loaders do not have USB driver, even Grub2. It means that having boot-loader on floppy ( it fits !) and kernel/initramfs on liveUSB doesn't work with Lilo/Syslinux/Grub{1,2}.

For this config to work you have to use a boot-loader *with* USB drivers, and of course this boot-loader exists and is well known, it's Linux kernel !: http://www.solemnwarning.net/kexec-loader/ will do the trick: it fits on a floppy ! When BIOS starts it, it loads a temporary linux kernel and initrd with USB drivers and in a second stage, the liveUSB kernel and initramfs is loaded and passes control to.

I have this config working with my liveUbuntu 9.10 built with live-helper, quite easy to do.


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