4.3. Preparing Files for USB Memory Stick Booting
| Chapter 4. Obtaining System Installation Media |

## 4.3. Preparing Files for USB Memory Stick Booting

To prepare the USB stick, you will need a system where GNU/Linux is already running and where USB is supported. With current GNU/Linux systems the USB stick should be automatically recognized when you insert it. If it is not you should check that the usb-storage kernel module is loaded. When the USB stick is inserted, it will be mapped to a device named `/dev/sdX`, where the “X” is a letter in the range a-z. You should be able to see to which device the USB stick was mapped by running the command dmesg after inserting it. To write to your stick, you may have to turn off its write protection switch.

| Warning
The procedures described in this section will destroy anything already on the device! Make very sure that you use the correct device name for your USB stick. If you use the wrong device the result could be that all information on for example a hard disk could be lost.

### 4.3.1. Preparing a USB stick using a hybrid CD or DVD image

Ubuntu CD and DVD images can now be written directly to a USB stick, which is a very easy way to make a bootable USB stick. Simply choose a CD or DVD image that will fit on your USB stick. See Section 4.1, “Official Ubuntu CD-ROMs” to get a CD or DVD image.

Alternatively, for very small USB sticks, only a few megabytes in size, you can download the `mini.iso` image from the `netboot` directory (at the location mentioned in Section 4.2.1, “Where to Find Installation Images”).

The CD or DVD image you choose should be written directly to the USB stick, overwriting its current contents. For example, when using an existing GNU/Linux system, the CD or DVD image file can be written to a USB stick as follows, after having made sure that the stick is unmounted:

    # cp debian.iso /dev/sdX
    # sync

The win32diskimager utility can be used under other operating systems to copy the image.

| Important
The image must be written to the whole-disk device and not a partition, e.g. /dev/sdb and not /dev/sdb1. Do not use tools like unetbootin which alter the image.

| Important
Simply writing the CD or DVD image to USB like this should work fine for most users. The other options below are more complex, mainly for people with specialised needs.

The hybrid image on the stick does not occupy all the storage space, so it may be worth considering using the free space to hold firmware files or packages or any other files of your choice. This could be useful if you have only one stick or just want to keep everything you need on one device.

Create a second, FAT partition on the stick, mount the partition and copy or unpack the firmware onto it. For example:

    # mount /dev/sdX2 /mnt
    # cd /mnt
    # tar zxvf /path/to/firmware.tar.gz
    # cd /
    # umount /mnt

You might have written the `mini.iso` to the USB stick. In this case the second partition doesn't have to be created as, very nicely, it will already be present. Unplugging and replugging the USB stick should make the two partitions visible.

### 4.3.2. Manually copying files to the USB stick

An alternative way to set up your USB stick is to manually copy the installer files, and also a CD image to it. Note that the USB stick should be at least 1 GB in size (smaller setups are possible if you follow Section 4.3.3, “Manually copying files to the USB stick — the flexible way”).

There is an all-in-one file netboot/boot.img.gz which contains all the installer files (including the kernel) as well as `syslinux` and its configuration file .

To use this image simply extract it directly to a partition on your USB stick:

    # zcat boot.img.gz > /dev/sdX1

### 4.3.3. Manually copying files to the USB stick — the flexible way

If you like more flexibility or just want to know what's going on, you should use the following method to put the files on your stick. One advantage of using this method is that — if the capacity of your USB stick is large enough — you have the option of copying any ISO image, even a DVD image, to it.

#### 4.3.3.1. Partitioning the USB stick

We will show how to set up the memory stick to use the first partition, instead of the entire device.

| Note

Since most USB sticks come pre-configured with a single FAT16 partition, you probably won't have to repartition or reformat the stick. If you have to do that anyway, use cfdisk or any other partitioning tool to create a FAT16 partition[2], install an MBR using:

    # install-mbr /dev/sdX

The install-mbr command is contained in the `mbr` Ubuntu package. Then create the filesystem using:

    # mkdosfs /dev/sdX1

Take care that you use the correct device name for your USB stick. The mkdosfs command is contained in the `dosfstools` Ubuntu package.

In order to start the kernel after booting from the USB stick, we will put a boot loader on the stick. Although any boot loader (e.g. `lilo`) should work, it's convenient to use `syslinux`, since it uses a FAT16 partition and can be reconfigured by just editing a text file. Any operating system which supports the FAT file system can be used to make changes to the configuration of the boot loader.

To put `syslinux` on the FAT16 partition on your USB stick, install the `syslinux` and `mtools` packages on your system, and do:

    # syslinux /dev/sdX1

Again, take care that you use the correct device name. The partition must not be mounted when starting syslinux. This procedure writes a boot sector to the partition and creates the file `ldlinux.sys` which contains the boot loader code.

#### 4.3.3.2. Adding the installer image

Mount the partition (`mount /dev/`sdX1` /mnt`) and copy the following installer image files to the stick:

- `vmlinuz` or `linux` (kernel binary)

- `initrd.gz` (initial ramdisk image)

You can choose between either the text-based or the graphical version of the installer. The latter can be found in the `gtk` subdirectory. If you want to rename the files, please note that `syslinux` can only process DOS (8.3) file names.

Next you should create a `syslinux.cfg` configuration file, which at a bare minimum should contain the following line (change the name of the kernel binary to “`linux`” if you used a `netboot` image):

    default vmlinuz initrd=initrd.gz

For the graphical installer you should add `vga=788` to the line. Other parameters can be appended as desired.

To enable the boot prompt to permit further parameter appending, add a `prompt 1` line.

If you used an `hd-media` image, you should now copy the ISO file of an Ubuntu ISO image[3] onto the stick. When you are done, unmount the USB memory stick (`umount /mnt`).

[2] Don't forget to set the “bootable” bootable flag.

[3] You can use either a netinst or a full CD image (see Section 4.1, “Official Ubuntu CD-ROMs”). Be sure to select one that fits. Note that the “netboot `mini.iso`” image is not usable for this purpose.

4.2. Downloading Files from Ubuntu Mirrors |  | 4.4. Preparing Files for Hard Disk Booting