Introduction to Customizing the BOS Install Program

The first time you install AIX, the Base Operating System (BOS) installation program presents menus from which you must choose setup options. This initial installation also automatically starts a post-installation configuration program, either the graphical Configuration Assistant or the ASCII Installation Assistant. Refer to "Customizing Your Installation" for more information about Configuration Assistant and Installation Assistant.

Note: A system with an ASCII interface will automatically start Installation Assistant as its post-installation configuration program.

For subsequent installations, you can change many aspects of the default BOS install program by editing the bosinst.data file. For example, by specifying no prompts, you can customize the program to install BOS without menus. You can also customize BOS installation to bypass Configuration Assistant or Installation Assistant and start your own configuration script. You can use the bosinst.data file to replicate one set of installation settings on other machines. For example, system administrators can create a bosinst.data file with settings that can be used to install all the machines they support that have the same configuration.

If you run your own configuration script from a bosinst.data file or from the Network Installation Manager (NIM), the environment in place at the time the script is run is a single-user environment. This environment is not available as a multi-user environment, and thus, there are limits to what can be run from a configuration script. The actual /etc/init is not running, so no process management is taking place. All available memory is not actually available because the RAM file system still exists, so devices that try to pin large amounts of memory to run may fail to configure. In addition, signal handling is not available.

In this environment, it is recommended that the following guidelines be followed for configuration scripts:

• Base devices can be configured, but devices that require daemons or more complex configuration should be started at reboot time by adding the necessary code to the end of the /etc/firstboot script.
• Daemons should not be started.
• Items such as NIS configuration, using system resource controller (SRC), and so on, should be done by creating a separate entry in /etc/inittab and running a configuration script at reboot time.
• No action should be taken that requires more than 32MB of paging space unless the paging space is implicitly increased.

Notes:

1. Another installation file, image.data, can also be modified and used during BOS installation. The image.data file contains information describing the image installed during the BOS installation process. This information includes the sizes, names, maps, and mount points of logical volumes and file systems in the root volume group. The installation program also takes input from the image.data file regarding defaults for the machine being installed. See AIX Version 4.3 Files Reference for a description of the image.data file. The procedure for using the bosinst.data file to customize BOS installation can also be used for the image.data file. The modified files can be used together to override BOS installation defaults.
2. You can also use the instructions in this chapter to create a supplemental diskette containing a modified preserve.list file, which is used during a Preservation Installation. For more information about the preserve.list file, see "Installation Methods".

The bosinst.data file directs the actions of the BOS installation program. The file resides in the /var/adm/ras directory on the installed machine only, and it is not accessible on the commercial tape or the CD-ROM on which you received AIX.

The bosinst.data file contains stanzas with variables set to default values. Each variable is on a new line, in the Variable=Value form. A blank line separates each stanza. The information in these stanzas informs the installation program about such things as the method and type of installation, the disks in the machine, and the language used. By editing the file with an ASCII text editor, you can substitute new values for the default variables.