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Accessing USB from commandline


From: sinan polat
Subject: Accessing USB from commandline
Date: Sun, 22 Jan 2012 22:24:35 +0200

Hi, I just joined the group to ask a question. I think it's a non-trivial one.

I am trying to install linux on an old laptop which:
- has a broken CDROM drive, it can't read installation CDs properly.
- has 248 MB memory.
- has an old BIOS which doesn't support booting from flash drive.
- has PXE booting.

What I tried so far:
- I used syslinux's gpxe and memdisk in a chained fashion to boot from an .iso file on another computer configured as DHCP and TFTP server. I used this solution before with better computers. But now it failed to load the ISO onto laptop's memory since iso file is larger than 248 MB.

- I booted the linux kernel inside the installation CD from gpxe. It works fine but setup CD's linux looks for the files in /dev/sr0 instead of TFTP server. It falls down to a shell in ramdisk, I can see the block devices on laptop, I guess I can see the files on TFTP server but I can't boot the kernel since I am already running a kernel.

- I tried to use GRUB2's PXE boot and then booting a kernel on a USB disk plugged into the laptop. I can reach GRUB's command line but when I enter ls I can't see any of the block devices. I can only see (pxe) device and ls doesn't show any files on the TFTP server. I can see USB ports when I run lspci but usb command shows nothing.

My question is how can I make GRUB see the local disk and better yet the flash drive on the laptop when I boot GRUB from PXE? I want to make a flash disk installation but I can't see any block devices. I tried to remove and insert back the modules but I guess that doesn't make a rescan. Even if the BIOS doesn't recognize USB drives I think I should have at least be able to see laptops disk, partitions and filesystems (right now there is a windows installation on the laptop).

BTW I learned so much meanwhile and in fact I'm curious about the booting process in general. I know a little bit C and 32bit assembly and if I have to code something I'd love to take this question to development mail list. It would be a nice little project for me.

I am planning to boot gparted iso (which is less than 248 MB) by using gpxe-memdisk combo I mentioned earlier then do some partitioning, copying contents of installation from flash disk, integrating a boot loader to the MBR and booting from a harddisk partition to install linux to a harddisk partition.

But I hope there is a better way, leaving all the setup issues to installer.

Thanks for reading, I hope it is not complicated. It was complicated for me but I hope there is an easy way around.

Sincerely,
Sinan



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