Ubuntu installer

The ubuntu-installer is an older version of the Debian installer. This page describes how it works in the Automated installation setup of Wikimedia.

Netboot

If the server is set to net boot, it requests network settings through DHCP at startup. The DHCP server assigns it an IP (which should be static in Wikimedia's setup) and gives it an IP address and filename of a TFTP server, where the server can retrieve its bootup files.

TFTP

The TFTP files consist of a PXELINUX image, which is "syslinux for netbooting". The config file used by PXELINUX is pxelinux.cfg, in the same directory as the PXELINUX image file pxelinux.0 itself. This configuration file consists of a number of different boot sets which specify a kernel and corresponding kernel parameters (boot options). The default automatic server install set is server, which should boot automatically after 10 seconds.

To automate the first part of the installation, a few parameters are included to the Linux kernel command line to suppress dialogs and questions until the Ubuntu installer can download its preseed configuration file, automating the rest of the install. These parameters are:

pkgsel/install-pattern=~t^ubuntu-standard$
rw preseed/url=http://www.knams.wikimedia.org/autoinstall/preseed.cfg
DEBCONF_DEBUG=5
debian-installer/locale=en_US
kbd-chooser/method=us
netcfg/choose_interface=auto
netcfg/get_hostname=unassigned

This specifies that the installer should skip the first questions about country, language and locale, and retrieve network settings using DHCP in order to download the preseed file. It will use the first interface with an established link, usually eth0.