This is an update of the article published before for Debian Sarge. This time, the preparation of an USB device for the installation of Debian Lenny is on the menu. Note that the Ubuntu Startup Disk Creator is not really useful to create a Debian installation device.

Insert an empty(!) USB device of at least 256MB, and look for it in dmesg:

$ dmesg

At the end of the output, it says:

[1922747.172561] sd 29:0:0:0: Attached scsi generic sg4 type 0
[1922747.179137] sd 29:0:0:0: [sde] 1959807 512-byte logical blocks:
(1.00 GB/956 MiB)
[1922747.179629] sd 29:0:0:0: [sde] Write Protect is off
[1922747.179637] sd 29:0:0:0: [sde] Mode Sense: 0b 00 00 08
[1922747.179643] sd 29:0:0:0: [sde] Assuming drive cache: write through
[1922747.182521] sd 29:0:0:0: [sde] Assuming drive cache: write through
[1922747.182532]  sde: sde1
[1922747.205897] sd 29:0:0:0: [sde] Assuming drive cache: write through
[1922747.205908] sd 29:0:0:0: [sde] Attached SCSI removable disk

So apparantly, this device is now known as "/dev/sde". Check if it's automagically mounted:

$mount

If it is (i.e. there is a line that contains /dev/sde), unmount this device first.

umount /dev/sde1

Download the current boot.img.gz from a Debian repository to your home directory. This assumes that you want to use the 64-bits version of Debian.

cd ~
wget ftp://ftp.debian.org/debian/dists/stable/main/installer-amd64/current/images/hd-media/boot.img.gz

Okay, now we need root privileges in order to put this image on the USB device:

sudo bash
zcat ~/boot.img.gz > /dev/sde

Mount the USB device on a mount point. In this case, /mnt/usbdisk will be used for that. Then copy the ISO file to this location.

sudo mkdir /mnt/usbdisk
sudo mount /dev/sde1 /mnt/usbdisk
wget http://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-506-amd64-netinst.iso -O /mnt/usbdisk/debian-506-amd64-netinst.iso

You may want to compare the SHA512SUMS of http://cdimage.debian.org/debian-cd/current/amd64/iso-cd/SHA512SUMS with your local version:

$ sha512sum /mnt/usbdisk/debian-506-amd64-netinst.iso

When they match, unmount this USB device, and remove it, because you are now ready to use it to install Debian from it.

$ cd
$ sudo umount /mnt/usbdisk

Original article: http://www.virtualconcepts.nl/2010/09/installing-debian-lenny-from-usb/