Kickstart

PXE doc

http://www.pix.net/software/pxeboot/archive/pxespec.pdf

Understanding PXE Booting and Kickstart Technology

https://docs.oracle.com/cd/E24628_01/em.121/e27046/appdx_pxeboot.htm#EMLCM12198

PXE works with Network Interface Card (NIC) of the system by making it function like a boot device. The PXE-enabled NIC of the client sends out a broadcast request to DHCP server, which returns with the IP address of the client along with the address of the TFTP server, and the location of boot files on the TFTP server. The following steps describe how it works:

 

1. Target Machine (either bare metal or with boot sector removed) is booted.
2. The Network Interface Card (NIC) of the machine triggers a DHCP request.
3. DHCP server intercepts the request and responds with standard information (IP, subnet mask, gateway, DNS etc.). In addition, it provides information about the location of a TFTP server and boot image (pxelinux.0).
4. When the client receives this information, it contacts the TFTP server for obtaining the boot image.
5. TFTP server sends the boot image (pxelinux.0), and the client executes it.
6. By default, the boot image searches the pxelinux.cfg directory on TFTP server for boot configuration files on the TFTP server using the following approach:
   First, it searches for the boot configuration file that is named according to the MAC address represented in lower case hexadecimal digits with dash separators. For example, for the MAC Address "88:99:AA:BB:CC:DD", it searches for the file 01-88-99-aa-bb-cc-dd.
   Then, it searches for the configuration file using the IP address (of the machine that is being booted) in upper case hexadecimal digits. For example, for the IP Address "192.0.2.91", it searches for the file "C000025B".
   If that file is not found, it removes one hexadecimal digit from the end and tries again. However, if the search is still not successful, it finally looks for a file named "default" (in lower case).
   For example, if the boot file name is /tftpboot/pxelinux.0, the Ethernet MAC address is 88:99:AA:BB:CC:DD, and the IP address 192.0.2.91, the boot image looks for file names in the following order:

   /tftpboot/pxelinux.cfg/01-88-99-aa-bb-cc-dd
   /tftpboot/pxelinux.cfg/C000025B
   /tftpboot/pxelinux.cfg/C000025
   /tftpboot/pxelinux.cfg/C00002
   /tftpboot/pxelinux.cfg/C0000
   /tftpboot/pxelinux.cfg/C000
   /tftpboot/pxelinux.cfg/C00
   /tftpboot/pxelinux.cfg/C0
   /tftpboot/pxelinux.cfg/C
   

7. The client downloads all the files it needs (kernel and root file system), and then loads them.
8. Target Machine reboots.
   The Provisioning application uses Redhat's Kickstart method to automate the installation of Redhat Linux on target machines. Using kickstart, the system administrator can create a single file containing answers to all the questions that will usually be asked during a typical Red Hat Linux installation.
   The host specific boot configuration file contains the location of the kickstart file. This kickstart file would have been created earlier by the stage directive of the OS image based on the input from user.

Kickstart sequence of events
http://www.linux-mag.com/id/6747/

A network-based kickstart can be initiated by an PXE Boot capable network card. The PXE Boot first requests an IP address from a DHCP server. It also obtains the location of a PXE Boot file from the DHCP server. PXELINUX is a bootloader for Linux using the PXE network booting protocol. The PXE Boot file is loaded from the TFTP server along with the contents of a file which defines the location and name of the installation kernel and initrd.img file as well as some parameters for the boot kernel and a menu for the Anaconda installer. This configuration file for Anaconda also contains the location of the kickstart configuration file to be used during the installation. 

The PXE Boot file then loads the boot kernel and initrd image still using TFTP. After booting, Anaconda is started and Anaconda loads the menu and displays a window with a timer with several menu options. The Menu and time-out can be skipped if you do not need to make any choices here. 

After choosing the desired kickstart installation, Anaconda locates the kickstart configuration file from the HTTP server and reads it. The kickstart configuration file has a default name of ks.cfg, but can be named anything. We use several for our different configurations, so provide unique names for each. If all of the data required to perform a complete installation is included in the kickstart configuration file, the installation completes without further intervention from the administrator. The RPM files used during the installation are downloaded from the HTTP server as they are needed.

The kickstart configuration file can also contain bash script commands that can be run both before and after the rest of the installation. We make extensive use of the post-installation bash scripts to perform installations of locally required RPM packages and tarballs as well as to make configuration changes before the first reboot.