The following installation guide is taken from the The Debian Administrator's Handbook
Step 1 - Booting and starting the installer
Once the BIOS has begun booting from the device (CD, DVD or USB), the isolinux bootloader menu appears:
At this stage, the Linux kernel is not yet loaded; this menu allows you to choose the kernel to boot and enter possible parameters to be transferred to it in the process. For a standard installation, you only need to choose “Install” or “Graphical install” (with the arrow keys), then press the Enter key to initiate the remainder of the installation process.
Once booted, the installation program guides you step by step throughout the process. This section presents each of these steps in detail.
Step 2 -Selecting the language
The installation program begins in Spanish, but the first step allows the user to choose the language that will be used in the rest of the process. Choosing French, for example, will provide an installation entirely translated into English (and a system configured in English as a result). This choice is also used to define more relevant default choices in subsequent stages (notably the keyboard layout).
Step 3 - Selecting the country
The second step consists in choosing your country. Combined with the language, this information enables the program to offer the most appropriate keyboard layout. This will also influence the configuration of the time zone. In the United States, a standard QWERTY keyboard is suggested, and a choice of appropriate time zones is offered.
Step 4 -Selecting the keyboard layout
The proposed “American English” keyboard corresponds to the usual QWERTY layout.
Step 5 - Configuring the keyboard
Select the keymap to use:
Step 6 - Detecting Hardware
This step is completely automatic in the vast majority of cases. The installer detects your hardware, and tries to identify the CD-ROM drive used in order to access its content. It loads the modules corresponding to the various hardware components detected, and then “mounts” the CD-ROM in order to read it. The previous steps were completely contained in the boot image included on the CD, a file of limited size and loaded into memory by the BIOS when booting from the CD.
The installer can work with the vast majority of drives, especially standard ATAPI peripherals (sometimes called IDE and EIDE). However, if detection of the CD-ROM reader fails, the installer offers the choice to load a kernel module (for instance from a USB key) corresponding to the CD-ROM driver.
Step 7 - Loading Components
With the contents of the CD now available, the installer loads all the files necessary to continue with its work. This includes additional drivers for the remaining hardware (especially the network card), as well as all the components of the installation program.
Step 8 - Configuring the hostname
Chose the system's hostname (gnuinos by default):
Step 9 - Creating the First User
the installer gives you the chance to create a standard user account with "sudo" permitions (i.e. with the posibility to perform tasks as a system's Administrators). o that the administrator doesn't get into the bad habit of working as root. The precautionary principle essentially means that each task is performed with the minimum required rights, in order to limit the damage caused by human error. This is why the installer will ask for the complete name of this first user, their username, and their password (twice, to prevent any entry error which would later be difficult to amend ).
Step 10 - Detecting Disks and Other Devices
This step automatically detects the hard drives on which Debian may be installed. They will be presented in the next step: partitioning.
Step 11 - The Partitioning Tool
The partitioning step is traditionally difficult for new users. It is necessary to define the various portions of the disks (or “partitions”) on which the Linux filesystems and virtual memory (swap) will be stored. This task is complicated if another operating system that you want to keep is already on the machine. Indeed, you will then have to make sure that you do not alter its partitions (or that you resize them without causing damage).
Fortunately, the partitioning software has a “guided” mode which recommends partitions for the user to make — in most cases, you can simply validate the software's suggestions.
The first screen in the partitioning tool offers the choice of using an entire hard drive to create various partitions. For a (new) computer which will solely use Linux, this option is clearly the simplest, and you can choose the option “Guided - use entire disk”. If the computer has two hard drives for two operating systems, setting one drive for each is also a solution that can facilitate partitioning. In both of these cases, the next screen offers to choose the disk where Linux will be installed by selecting the corresponding entry (for example, “SCSI1 (0,0,0) (sda) - 48.3 GB ATA VBOX HARDDISK”). You then start guided partitioning.
Guided partitioning can also set up LVM logical volumes instead of partitions (see below). Since the remainder of the operation is the same, we will not go over the option “Guided - use entire disk and set up LVM” (encrypted or not).
In other cases, when Linux must work alongside other already existing partitions, you need to choose manual partitioning.
Step 12 - Installing the System
This step, which doesn't require any user interaction, installs tue system in the target.
Step 13 - Choosing the kernel (only in x86 arquitecture)
This step allows you to choose the arquitecture of the kernel between i586 and i686-pae:
Step 14 - Installing the GRUB Bootloader
The bootloader is the first program started by the BIOS. This program loads the Linux kernel into memory and then executes it. It often offers a menu that allows the user to choose the kernel to load and/or the operating system to boot.
Step 15 - Finishing the Installation and Rebooting
The installation is now complete, the program invites you to remove the CD-ROM from the reader and to restart the computer.
The GRUB Bootloader