Ubuntu installer
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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 <tt>eth0</tt>. | 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 <tt>eth0</tt>. | ||
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| + | === Download preseed configuration === | ||
| + | After the installer has detected the network interfaces and retrieved network settings through DHCP, it attempts to download the <tt>preseed.cfg</tt> over HTTP. Based on <tt>include</tt> directives in the <tt>preseed.cfg</tt>, it will download other included files as well, possibly depending on the cluster, the specific server or its task. | ||
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| + | The preseed files are text files in <tt>debconf --set-selections</tt> format, that specify variables and their values which will be set in advanced (preseeded). These variables correspond to questions that are normally asked by the installer, but which will be skipped when preseeded with correct values. | ||
Revision as of 14:28, 24 September 2006
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.
Download preseed configuration
After the installer has detected the network interfaces and retrieved network settings through DHCP, it attempts to download the preseed.cfg over HTTP. Based on include directives in the preseed.cfg, it will download other included files as well, possibly depending on the cluster, the specific server or its task.
The preseed files are text files in debconf --set-selections format, that specify variables and their values which will be set in advanced (preseeded). These variables correspond to questions that are normally asked by the installer, but which will be skipped when preseeded with correct values.
