Following steps are performed during an installation after the linux kernel has booted on the install clients.
You can also define additional programs or scripts, that will be run on particular occasions. They are called hooks. Hooks can add additional functions to the installation process or replace the default subtasks of FAI. So it's very easy to customize the whole installation process. Hooks are explained in detail in Hooks, Section 6.11.
The installation time is mainly determined by the amount of software that will be installed. A dual Pentium II, 400 MHZ with 128 MB RAM and a 10 Mbit network card needs about 11 min when installing 520 MB of software to local disk. An installation with 90 MB software (a dataless client) only needs two minutes. The checking for bad blocks on a 4 GB partition needs additional 6 minutes. Using a 100 Mbit LAN does not decrease the installation time considerable, so the network will not be the bottleneck when installing several clients simultaneously.
After the install client has booted, only the script
/sbin/rcS_fai[14] is
executed. This is the main script, that controls the sequence of tasks for
FAI. No other scripts in /etc/init.d/ are executed.
A ramdisk is created and mounted to /tmp, which is the only
writable directory, until local filesystems are mounted. Additional parameters
are received from the BOOTP or DHCP daemon and the configuration space if
mounted via NFS from the install server to /fai. The setup is
finished after additional virtual terminals are created and the secure shell
daemon for remote access is started on demand.
Now scripts in /fai/class/ are executed to define classes and
variables that are later used in the site specific configuration scripts. All
scripts matching S[0-9]*.{sh,pl} are executed in alphabetical
order. Every word that these scripts print to the standard output are
interpreted as class names. These classes are defined for this install client.
You can also say this client belongs to these classes. A class is defined or
undefined and has no value. Only defined classes are of interest for an
install client. A description of all classes can be found in
/usr/share/doc/fai/classes_description.txt. It is advisable to
document the job a new class performs. Then, this documentation is the base
for composing a configuration from classes.
The scripts S05modules.sh loads kernel modules on demand. So you
can use classes when loading modules and also define more classes after the
kernel has loaded modules and recognized new hardware. A complete description
of all these scripts can be found in Scripts in /fai/scripts, Section
6.9.
After defining the classes, every file matching *.var, which prefix is a defined class, is executed to define variables.
Then exactly one disk configuration file from /fai/disk_config is
selected using classes. It's the description how all the local disks will be
partitioned, which filesystems should be created and how they are mounted.
It's also possible to preserve the disk layout or to preserve the data on a
partition. It's done by the command setup_harddisks, which uses
sfdisk for partitioning. The format of the configuration file is
described in /usr/share/doc/fai/README.disk_config.
During the installation process all local filesystems are mounted relative to
/tmp/target . So, for e.g. /tmp/target/home will
become /home in the new installed system.
When local filesystems are created, they are all empty (except for preserved
partitions). Now the Debian base system and all requested software packages
are installed on the new filesystems. First the base archive is unpacked, then
the command install_packages installs all packages using
apt-get(8) without any manually interaction needed. If a packages
requires an other packages it resolves this dependency by installing the
required package.
Classes are also used when selecting the configuration files in
/fai/package_config/ for software installation. The format of the
configuration files is described in Software package configuration, Section
6.8.
After all requested software packages are installed, the system is nearly ready
to go. But not all default configurations of the software packages will meet
your site specific needs. So you can call arbitrary scripts, which adjust the
system configuration. Therefore scripts, that match a class name in
/fai/scripts[15] will
be executed. FAI comes with some templates for these scripts, but you can
write your own Bourne, bash, perl, cfengine or expect scripts.
These important scripts are described in detail in Scripts in /fai/scripts, Section 6.9.
When all installation tasks are finished, the log files are written to
/var/log/fai/$HOSTNAME/install/ [16] on the new system and to the a account on the install
server, if $LOGUSER is defined in /etc/fai.conf.
At least the system is automatically rebooted if the flag reboot is
set [17]. This is only useful if
booting from network card or if you can change the boot device using the
command bootsector. Otherwise, you have to remove the floppy disk
and type return or call faireboot from a remote login. You must
change the boot device, to boot the new installed system otherwise the
installation would be performed again. Read Changing the boot device, Section 6.10
how to change the boot device.
lange@informatik.uni-koeln.de