Kapitel 4. Installation

För att kunna använda Debian behöver du först installera det på en dator; detta hanteras av installationsprogrammet för Debian. En komplett installation involverar många åtgärder. Detta kapitel syftar till att gå igenom dessa i kronologisk ordning.

The installer for Bookworm is based on debian-installer. Its modular design enables it to work in various scenarios and allows it to evolve and adapt to changes. Despite the limitations implied by the need to support a large number of architectures, this installer is very accessible to beginners, since it assists users at each stage of the process. Automatic hardware detection, guided partitioning, and graphical user interfaces have solved most of the problems that novices used to face in the early years of Debian.

Installation requires 256 MB of RAM (Random Access Memory) and at least 2 GB of hard drive space. All Falcot computers meet these criteria. Note, however, that these figures apply to the installation of a very limited system without a graphical desktop. A minimum of 2 GB of RAM and 10 GB of hard drive space are really recommended for a basic office desktop workstation.

BEWARE Upgrading from Bullseye

If you already have Debian Bookworm installed on your computer, this chapter is not for you! Unlike other distributions, Debian allows updating a system from one version to the next without having to reinstall the system. Reinstalling, in addition to being unnecessary, could even be dangerous, since it could remove already installed programs.

Uppdateringsprocessen finns beskriven i Avsnitt 6.7, ”Uppgradering från en stabil distribution till nästa”.

Upgrading from even older Debian systems directly is not supported. In this case you need to update gradually to the stable release which followed your Debian version, and so on. Previous versions of this book will assist you in that matter.

4.1. Installations Metoder

A Debian system can be installed from several types of media, as long as the BIOS/UEFI (see NOTERA UEFI, en modern ersättare för BIOS) of the machine allows it. You can for instance boot with a CD-ROM, a USB key, or even through a network.

4.1.1. Installera från en CD-skiva/DVD-skiva

Den mest använda installationsmetoden är från en CD-skiva (eller DVD-skiva vilket fungerar på samma sätt): datorn startar upp från skivan och installationsprogrammet tar sen över.

Various CD-ROM families have different purposes: netinst (network installation) contains the installer and the base Debian system; all other programs are then downloaded. Its “image”, that is the ISO-9660 filesystem that contains the exact contents of the disk, takes up about 310 to 780 MB (depending on the architecture). On the other hand, the complete set offers all packages and allows for installation on a computer that has no Internet access; it requires around 21 DVD-ROMs (or 5 Blu-ray disks). There is no more official CD-ROMs set as they were really huge, rarely used and now most of the computers use DVD-ROMs as well as CD-ROMs. But the programs are divided among the disks according to their popularity and importance; the first disk will be sufficient for most installations, since it contains the most used software.

HISTORY Firmware in installation media

The size of the netinst installation images has increased significantly with the release of Debian Bookworm. They now include packages containing proprietary firmware files to run specific hardware devices like network cards. In previous releases, these files had to be downloaded separately, or an alternative, but unofficial netinst image had to be used. This has been a major change in the Debian project's historic treatment towards its installers, but also a major gain for Debian's users.

There is a last type of image, known as mini.iso, which is only available as a by-product of the installer. The image only contains the minimum required to configure the network and everything else is downloaded (including parts of the installer itself, which is why those images tend to break when a new version of the installer is released). Those images are usually smaller than 100MB, and they can be found on the normal Debian mirrors under the dists/release/main/installer-arch/current/images/netboot/ directory.

To acquire Debian CD-ROM images, you may, of course, download them and burn them to disk. You may also purchase them, and, thus, provide the project with a little financial support. Check the website to see the list of DVD-ROM image vendors and download sites.

→ https://www.debian.org/CD/

4.1.2. Starta upp från en USB-sticka

Efterssom de flesta datorer har möjlighet att starta upp från en USB-enhet så finns oftast möjligheten att installera Debian med en USB-sticka (portabel lagringsenhet i mindre format, flashminne).

Installationsmanualen förklarar hur man skapar en USB-sticka innehållande installationsprogrammet för Debian. Tillvägagångssättet är väldigt enkelt efterssom ISO avbilden för både i386 och amd64 processorarkitekturerna är hybridavbilder som kan startas upp från en CD-skiva lika väl som från en USB-sticka.

You must first identify the device name of the USB key (ex: /dev/sdb); the simplest means to do this is to check the messages issued by the kernel using the dmesg command. Then you must copy the previously downloaded ISO image (for example, debian-12.0.0-amd64-netinst.iso) with the command cat debian-12.0.0-amd64-netinst.iso >/dev/sdb; sync. This command requires administrator rights, since it accesses the USB key directly and blindly erases its content.

A more detailed explanation is available in the installation manual. Among other things, it describes an alternative method of preparing a USB key that is more complex, but that allows you to customize the installer's default options (those set in the kernel command line).

→ https://www.debian.org/releases/stable/amd64/ch04s03

4.1.3. Installation med hjälp av uppstart över nätverk

Många datorers BIOS system tillåter uppstart från ett nätverk genom att ladda ner en kärna och ett minimalt filsystemsavbild. Den här metoden (som har många namn, t.ex.PXE- eller TFTP-uppstart) kan rädda dagen ifall datorn saknar CD-spelare, eller om BIOS inte kan starta upp från andra media.

Den här installationsmetoden utförs i två steg. Första steget sker när datorn skall till att starta upp, då BIOS (eller nätverkskortet) utfärdar en BOOTP/DHCP begäran för att automatiskt erhålla en IP-adress. När en BOOTP eller DHCP server skickar tillbaka ett svar så inkluderar det ett filnamn så väl som nätverksinställningar. Efter att ha ställt in nätverkskonfigurationen så utfärdar klientdatorn en TFTP (Trivial Filöverföringsprotokoll) begäran om filen vars namn den tidigare erhöll. När filen erhållits så körs den som om den vore en uppstartsladdare. Den i sin tur startar upp Debians installationsprogram som om den kördes från en hårddisk, CD-skiva eller USB-sticka.

Alla detaljer kring den här metoden finns tillgänglig i installationsguiden (kapitel "Förbered filer för TFTP nätuppstart").

→ https://www.debian.org/releases/stable/amd64/ch05s01#boot-tftp-x86

→ https://www.debian.org/releases/stable/amd64/ch04s05

4.1.4. Andra Installationsmetoder

When we have to deploy customized installations for a large number of computers, we generally choose an automated rather than a manual installation method. Depending on the situation and the complexity of the installations to be made, we can use FAI (Fully Automatic Installer, described in Avsnitt 12.3.1, ”Helautomatisk installation (FAI)”), or even a customized installation DVD with so-called “preseeding“ (see Avsnitt 12.3.2, ”Preseeding Debian-Installer”).

It should also be noted that the installer can load and run an SSH server and thus provides the ability to install Debian remotely via an SSH session. The release notes also describe how to run the installer from an existing system using grub to replace it completely.