4.3. Tiedostojen valmistelu käynnistettäessä USB-muistilta

To prepare the USB stick, we recommend to use 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.

[Varoitus] Varoitus

Tässä osiossa kuvatut toiminnot tuhoavat kaiken mitä laitteella jo on. Varmistu käyttäväsi USB-muistin oikeaa laitenimeä. Jos käytät väärää laitenimeä, saatat tuhota kaiken tiedon esimerkiksi koneen kiintolevyltä.

4.3.1. Preparing a USB stick using a hybrid CD/DVD image

Debian installation images can now be written directly to a USB stick, which is a very easy way to make a bootable USB stick. Simply choose an image (such as the netinst, CD, DVD-1, or netboot) that will fit on your USB stick. See Kohta 4.1, ”Official Debian GNU/Linux installation images” to get an installation 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 Kohta 4.2.1, ”Where to Find Installation Files”).

The installation 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 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

Information about how to do this on other operating systems can be found in the Debian CD FAQ.

[Tärkeää] Tärkeää

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.

[Tärkeää] Tärkeää

Simply writing the installation 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 an installation image to it. Note that the USB stick should be at least 1 GB in size (smaller setups are possible if you follow Kohta 4.3.3, ”Manually copying files to the USB stick — the flexible way”).

Tarjolla on kaikki-yhdessä-tiedostossa -paketti hd-media/boot.img.gz, jossa on kaikki asentimen tiedostot (myös ydin) sekä syslinux että ja asetustiedosto .

Vaikka tämä tapa on mukava, kannattaa huomata sen vakava haitta: laitteen looginen koko rajoitetaan 1 Gtavuun, vaikka USB-muisti olisi suurempi. USB-muistille on tehtävä uudet osiot ja uudet tiedostojärjestelmät jotta sen täysi koko saadaan taas käyttöön jos sitä joskus halutaan käyttää johonkin muuhun.

Jos käytät tätä otosta, riittää purkaa se sellaisenaan USB-muistille:

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

After that, mount the USB memory stick (mount /dev/sdX /mnt), which will now have a FAT filesystem on it, and copy a Debian ISO image (netinst or full CD/DVD) to it. Unmount the stick (umount /mnt) and you are done.

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. Osioiden teko USB-muistille

Nyt näytetään miten käytetään USB-muistin ensimmäistä osiota eikä koko muistia.

[Huomaa] Huomaa

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[3], install an MBR using:

# install-mbr /dev/sdX

The install-mbr command is contained in the mbr Debian 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 Debian 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 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.

syslinux saadaan tallennettua FAT16-osioon USB-muistille asentamalla paketit syslinux ja mtools järjestelmään, ja antamalla komento:

# syslinux /dev/sdX1

Tarkista taas huolellisesti, että laitenimi on oikein. Osio ei saa olla liitettynä kun syslinux käynnistetään. Komento kirjoittaa osioon käynnistyssektorin ja luo tiedoston ldlinux.sys, jossa on käynnistyslataimen koodi.

4.3.3.2. Asentimen levyotoksen lisääminen

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 a Debian ISO image[4] onto the stick. When you are done, unmount the USB memory stick (umount /mnt).



[3] Don't forget to set the bootable bootable flag.

[4] You can use either a netinst or a full CD/DVD image (see Kohta 4.1, ”Official Debian GNU/Linux installation images”). Be sure to select one that fits. Note that the netboot mini.iso image is not usable for this purpose.