howto get my usb storage device on the bootoader without wiping off the previous boot
 

as Subjecy

You might want to indicate whether you use grub or lilo.

For grub, duplicate one of the stanzas in /boot/grub/menu.lst and edit it to suit. You may want to use the form like "root=/dev/disk/by-id/scsi-SATA_FUJITSU_MHU2100_NQ07T4825B7P-part6" rather then a /dev/sda# entry in the "kernel" line, because a usb drive may use a different device at a latter time. You will have to have the device present when updating grub. I'm not entirely certain if grub will be able to see the usb drive. This may also be BIOS dependent.

Here is a thread I wrote a few days ago telling how to put Grub into floppy, pen drive, CD/DVD or hard disk.

You only get a Grub prompt out of it but there is no PC system I know that cannot be booted up manually by a Grub prompt. By adding a menu.lst in the /boot/grub directory of the booting media you can boot Oses automatically.

Grub will be able to see USB devices if the USB legacy support is enabled in the Bios.

If you want to put two boot loaders into a USB storage device then have two partitions and put one boot loader in each one.

How to make a bootable floppy for Grub (universal)
 

To saikee,
went ok till Igot to the end oline including 'stage1' ending in /boot/grub. it returned an error message saying I had not surficiently specified a directory and suggested ' --sparse=never' this i tried but got another error message suggesting I had not mane the 'mkdir'correctly. This possible but had followed your instuctions to the letter. Are there diferrent unix commands in diferent kernals? Mine is Mandriva 2.6.17 (with updates-Mot developmental). any ideas?

Thanks'
Roy.

Can you show the output of
?

You need to adjust the name of the partition of the USB device to suit your case

usb made bootable
 

sorry to be ignorant but made it bootable following install instructions in Fedora 5 Bible and installed said thing in usb which worked and rebooted but the hard drive did not so do I edit the /etc/fstab which was denied even under su (both systems are Fedora) or the bootloader using something like supergrub or sysre.ccd.org , if so how?
Roy
Appologies.

re re etc
 

Don't want to use F disck as it can bugger up everything.