now i’ll explain how to install ubuntu without using cdrom and with a usb flash memory:
a usb flash memory by default is formatted in vfat file system, i will not change the file system type.
– first you need to create a master boot record in the flash memory
$ sudo parted /dev/sdb set 1 boot on
you need to change sdb to you usb device, you can know what is the link to your device from the command mount
now you have a bootable usb storage device all what you need next is to copy the kernel and init parameters file in the suitable place in your flash memory.
– create a directory named casper in root of your flash memory.
– download the following files and put them in the directory named casper
– get the iso image which will be used to install ubuntu, you need to download the alternative CD not the normal cd.
– extract the iso image and copy the folder isolinux from the extracted iso to the root of usb flash memory.
– rename the isolinux folder in the root of the flash memory to syslinux.
– inside the syslinux folder rename the file isolinux.cfg to syslinux.cfg
– copy the alternative cd iso image -not the extracted folder- to the folder casper on the flash memory.
everything now is fine and you can reboot that machine and boot from the usb flash memory then install ubuntu.