UNetbootin is a simple open source tool that allows you to install a variety of distributions over the Internet, without burning a CD.
The Wubi tool for installing Ubuntu this way has been around for a while, but unlike UNetbootin, Wubi installs Ubuntu on a file stored in a Windows environment and creates no actual partitions. UNetbootin will create a partitioned dual-boot system as though you installed with a CD. It's useful if you're working on a machine with a slow or no CD/DVD drive or don't have any spare discs to burn.
UNetbootin works using an installer program to add an entry to the bootloader in use (either GRUB or Windows' bootmgr, bcdedit or boot.ini) that boots a netboot kernel, which then downloads and installs your distribution of choice through your Internet connection.
How to install
To install a distribution you need to go to the UNetbootin site and get either a .deb, .rpm, or .exe installed, depending on which system you have and which you'd like to install. The packages available as of now are for Ubuntu, Fedora, Mandriva, openSUSE, CentOS, Arch Linux, Slackware, and Debian. The creators of UNetbootin say it's easy to modify UNetbootin to install any distribution, as long as it uses an unmodified netboot kernel and initrds. You can even spin your own custom distro and use your own local area network to install it. A small guide can be found on the site.
The installation process differs from distribution to distribution, particularly where you need to point the installer to get the files for the installation. For example, when installing Fedora, you need to choose FTP as the installation source and provide a custom server (listed at the UNetbootin site). However, when installating openSUSE, you need to select Network and HTTP as the source. Read the instructions on the site thoroughly before installing.
After installing the downloaded file, reboot your machine. You will be greeted either by a GRUB screen with an added entry, if you're using Linux, or a Windows-style dual boot window with a choice of either Windows or UNetbootin. Here you should choose the new UNetbootin option, and an installer will boot and you can install the operating system you want as you normally would, except that the installer downloads the files instead of reading them from a CD/DVD. You'll get all the regular options, including one to let you resize your partitions if necessary.
UNetbootin should create a dual-boot system, but if the original system you installed from was Windows, then choosing Windows from the new GRUB menu will drop you to the choice between Windows or the installer. When you first boot into Windows, UNetbootin will ask if you want to remove the installer from the system automatically.
In addition to creating a dual-boot system, UNetbootin can install a primary OS as well. If you have a machine that doesn't have an OS on it already, download the Debian minimal-install diskettes to install a minute system. Once that's set up, installing UNetbootin is as easy as using the command
Some distributions (such as Fedora, openSUSE, Mandriva, and Arch) allow you to use your hard drive as an UNetbootin installation media. This is helpful if you have the ISO file but no media burner. In such a case, select Hard Drive as the installation source. If you use this method, however, you can't resize the partition from which you install during the installation.
The UNetbootin site describes a number of other uses for the tool. One of the more interesting is to utilize UNetbooting to load an application rather than a distro, which opens the door for a host of new uses. For instance, you could boot into Parted Magic, a tool for formatting, repairing, and resizing partitions, or load Smart Boot Manager, which lets you boot from CD-ROM or diskette on computers with a faulty BIOS.
The site also contains information on installing other distros than the ones supported and accomplishing various other tasks using UNetbootin.
Whether you're installing Linux to liven up an older machine or a super-portable laptop with no available CD-ROM driver, or you don't have access to a capable media writer, or simply need to restore your computer, UNetbootin is a tool that can help you in numerous ways.