Els administradors de Falcot Corp, com molts altres administradors de grans serveis de TI, necessiten eines per instal·lar (o reinstal·lar) ràpidament, i automàticament si és possible, les seves noves màquines.

Aquests requisits es poden complir amb una àmplia gamma de solucions. D'una banda, eines genèriques com SystemImager ho gestionen mitjançant la creació d'una imatge basada en una màquina de plantilles, llavors es desplega aquesta imatge als sistemes de destinació; a l'altre extrem de l'espectre, l'instal·lador estàndard de Debian es pot «preseed» (“pre-sembrar”) amb un fitxer de configuració que dona les respostes a les preguntes plantejades durant el procés d'instal·lació. A mig camí, una eina híbrida com FAI («Fully Automatic Installer» o “instal·lador completament automatitzat”) instal·la màquines utilitzant el sistema de paquets, però també utilitza la seva pròpia infraestructura per a tasques que són més específiques per a desplegaments massius (com ara inici, particionat, configuració, etc.).

Each of these solutions has its pros and cons: SystemImager works independently from any particular packaging system, which allows it to manage large sets of machines using several distinct Linux distributions. It also includes an update system that doesn't require a reinstallation, but this update system can only be reliable if the machines are not modified independently; in other words, the user must not update any software on their own, or install any other software. Similarly, security updates must not be automated, because they have to go through the centralized reference image maintained by SystemImager. This solution also requires the target machines to be homogeneous, otherwise many different images would have to be kept and managed (an amd64 image won't fit on a powerpc machine, and so on).

On the other hand, an automated installation using debian-installer can adapt to the specifics of each machine: the installer will fetch the appropriate kernel and software packages from the relevant repositories, detect available hardware, partition the whole hard disk to take advantage of all the available space, install the corresponding Debian system, and set up an appropriate bootloader. However, the standard installer will only install standard Debian versions, with the base system and a set of pre-selected “tasks”; this precludes installing a particular system with non-packaged applications. Fulfilling this particular need requires customizing the installer… Fortunately, the installer is very modular, and there are tools to automate most of the work required for this customization, most importantly simple-cdd (CDD being an acronym for Custom Debian Derivative). Even this solution, however, only handles initial installations; this is usually not a problem since the APT tools allow efficient deployment of updates later on.

We will only give a rough overview of FAI, and skip SystemImager altogether (which is no longer in Debian, but available as a third-party package), in order to focus more intently on debian-installer and simple-cdd, which are more interesting in a Debian-only context.

d-i netcfg/hostname string worker
d-i netcfg/hostname seen false

menuentry --hotkey=i 'Install' {
    set background_color=black
    linux    /install.amd/vmlinuz preseed/file=/cdrom/preseed.cfg locale=en_US.UTF-8 keymap=us language=us country=US vga=788 --- quiet 
    initrd   /install.amd/initrd.gz
}

label install
        menu label ^Install
        kernel [...]
        append preseed/file=/cdrom/preseed.cfg locale=en_US.UTF-8 keymap=us language=us country=US vga=788 initrd=/install.amd/initrd.gz --- quiet

default vmlinuz
append preseed/file=/hd-media/preseed.cfg locale=en_US.UTF-8 keymap=us language=us country=US vga=788 initrd=initrd.gz  --