Debian installation from memory stick
Note: if you have access to a running Ubuntu of at least version 9.04 then you can use the "USB Startup Disk Creator" option in the Administration menu to create a bootable USB device from an ISO instead of using the procedure.
Many servers these days come without any floppy or CD/DVD drive. In this case the simplest means of installing Debian is using a USB memory stick - in fact this procedure is often more convenient than using a CD or DVD to install even if the system does have a drive to read them. First ensure you're running as the root user for this procedure, then insert the memory stick and check what device it is using dmesg or mount, then unmount it with the umount command.
Next download a Debian boot image and write it to the device (we'll assume the device is /dev/sdb here). Note that all the information on the USB device will be deleted by this operation.
wget ftp://ftp.debian.org/debian/dists/lenny/main/installer-amd64/current/images/hd-media/boot.img.gz zcat boot.img.gz > /dev/sdb
Now mount the image to a location in the filesystem:
mkdir debian-install mount /dev/sdb debian-install
Now download a Debian CD image and copy it into the USB device, then unmount and remove ready for booting in the target machine. Note that only the netinst and businesscard ISO's are small enough to fit on the USB partition because it is limited to 256MB regardless of the physical storage available on the device. Download from here: http://www.debian.org/CD/netinst/
cd debian-install wget ftp://ftp.iinet.net.au/pub/debian-cd/current/amd64/iso-cd/debian-501-amd64-netinst.iso umount /dev/sdb
You should now be able to set the target machine's BIOS to boot from USB, insert the device, start it up and go through the installation procedure as usual.