Gli amministratori della Falcot Corp, come molti amministratori di grandi servizi IT, hanno bisogno di strumenti per installare (o reinstallare) rapidamente e se possibile automaticamente le loro nuove macchine.

Questi requisiti possono essere soddisfatti da una vasta gamma di soluzioni. Da un lato, strumenti generici come SystemImager gestiscono il compito creando un'immagine basata su una macchina modello, quindi allestiscono quell'immagine sui sistemi destinazione; dall'altro lato dello spettro, l'installatore standard di Debian può essere preimpostato con un file di configurazione che dà le risposte alle domande poste durante il processo di installazione. A metà strada, uno strumento ibrido come FAI (Fully Automatic Installer) installa le macchine usando il sistema di pacchettizzazione, ma usa anche la propria infrastruttura per compiti più specifici su allestimenti di massa (come avviare, partizionare, configurare e così via).

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  --