Basefiles

One of FAI's peculiarities is the use of basefiles to install different distributions. I already mentioned that FAI is available not only for Debian and Ubuntu, but for CentOS and potentially any other operating system – as long as it is based on Linux. Therefore, you cannot rely on the installation mechanisms provided by the distributions.

Although, in Debian, installation would be possible with debconf and cdebconf, other distributions simply do not have a separate tool to take care of the system and its base installation. FAI therefore delivers basefiles for various distributions that contain a reduced basic system, which the FAI installer simply copies onto the disk.

Although the FAI developers regularly maintain these basefiles, it can take some time, so if you feel called upon to support the developers in this mammoth task, your desires certainly won't fall on deaf ears (Figure 4).

Figure 4: Basefiles for distributions are maintained by the people at FAI.

By the way, the FAI project can't completely hide its preferences, because at least one strictly Debian-specific feature has found its way into FAI. Preseeding of debconf makes possible the automatic configuration of many settings via Debian's system-wide framework for specifying configuration parameters for packages. If you simply store a debconf configuration for a class, when FAI then installs packages on the respective system, it automatically inherits all the debconf entries.

Saving Logs

The FAI developers are well aware of the need to back up logfiles created during system installation. At the end of an installation process initiated by FAI, FAI copies the 10 central logfiles from the minimal Debian system to the FAI server so that they are available to peruse later.

The same function also exists if you use FAI to update your systems centrally. The logs then contain the output produced during this step. The power of FAI with centralized updates should not be underestimated; several tests have shown in the past that a basic update by FAI with its basefiles works just as well as an update by the package manager.

By the way, environments without PXE do not have to forgo the benefits of FAI, because fai-mirror lets you to create an ISO file based on a local setup that can then be saved on a CD or USB stick and used as a local boot medium on the servers. You can thus avoid the whole topic of DHCP, TCP/IP, and UDP, the price being that you can't quickly tweak the configuration on the NFS server.

Conclusions

Although FAI is by no means the latest tool, it is at the height of its powers. If you want to roll out many servers quickly and easily, FAI is a reliable choice. Building a working preseed configuration for Debian and running a Kickstart environment for CentOS would be far more complex than the comparable overhead of FAI. The biggest difference between the systems would be the list of additional packages (Figure 5).

Figure 5: Package selection is easily the most distinct feature of the individual distributions.

FAI may be an oldie, but it is definitely still a goodie.

The Author

Martin Gerhard Loschwitz is a Telekom Public Cloud Architect for T-Systems and primarily works on topics such as OpenStack, Ceph, and Kubernetes.