Booting up Linux from a USB flash drive

Building the USB flash drive

You can build your bootable USB flash drive on Windows, but that is a slow procedure. So I show you how to build it on Linux. Ok, let's start! First, login as root and create a unique bootable partition by means of the 'cfdisk' command:

1) $ su root
2) # cdisk /dev/sda1

Exploring the cfdisk's menu, you will be able to find the suitable commands to partition your USB flash drive (type 'man cfdisk' to get help for the cfdisk command). After partitioning the USB flash drive you have to format it (I suggest you the FAT 16 filesystem):

# mkfs.vfat -n anyname -F 16 /dev/sda1

or even:

# mkdosfs /dev/sda1

Now download the DSL distribution's (Damn Small Linux) iso file at http://www.damnsmalllinux.org/ (choose the 'current' version). First you must create a folder to mount the iso file:

3) # mkdir tmp_iso

mount the iso file:

4) # mount -o loop dsl-0.8.3.iso tmp_iso

create another folder to mount your USB flash drive:

5) # mkdir /mnt/sda

mount the USB flash drive (sda1 should be the first USB device recognized by Linux):

6) # mount -t vfat /dev/sda1 /mnt/sda

copy the iso file to the mounted USB flash drive:

7) # cp -ra tmp_iso/* /mnt/sda/

go on with the following steps:

8) # cd /mnt/sda/boot
9) # cp vmlinuz /mnt/sda
10) # cp initrd.gz /mnt/sda
11) # cd /mnt/sda
12) # mv isolinux.bin syslinux.bin
13) # mv isolinux.cfg syslinux.cfg

now you must edit the 'syslinux.cfg' file to remove '/boot' from both '/boot/vmlinuz' and '/boot/initrd.gz' lines:

14) # pico syslinux.cfg (or even vi syslinux.cfg)

save the modified file. Now:

15) # cd..

16) # umount /mnt/sda

finally, download 'syslinux' at:

http://www.kernel.org/pub/linux/utils/boot/syslinux/

If you have problems compiling it, just install the syslinux.deb package by means of the 'apt' command. If you are not a Debian user, you can download the RPM package at:

http://www.kernel.org/pub/linux/utils/boot/syslinux/RPMS/

or visit an alternate site:

http://freshmeat.net/projects/syslinux/

After downloading/installing syslinux you must write the MBR sector on the USB flash drive. Just type:

# syslinux -s /dev/sda1

Congratulations, you have just built your Linux bootable USB flash drive! :o)

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