Graphical installer frontend

WORK IN PROGRESS. DO NOT USE ON SYSTEMS WITH VALUABLE DATA AS IT MAY OVERWRITE THE CONTENTS OF YOUR DISK. This is a temporary home until this is properly tested and integrated.

Theory of operation

The graphical installer frontend is an assistant (wizard) that guides the user through the installation. It consists of multiple pages.
None of the actual "business logic" (the actual installer) is implemented in the graphical installer frontend. Instead, a shell script is called to perform the installation.
The graphical installer frontend shows a progress bar during installation. This is calculated by bytes on the target disk divided by bytes needed
When the disk selection screen is shown, the graphical installer frontend will invoke the shell script with INSTALL

Environment variables

Environment variables are the proposed way for communicating back and forth between the installer script and the graphical installer frontend.

For retrieving the required space on the target disk

INSTALLER_PRINT_MIB_NEEDED=YES

When this is present, the installer must respond with just the number of bytes required on the target disk, e.g., INSTALLER_MIB_NEEDED=2158. The installer script must write this to stderr and then exit with no further action.

For performing the installation

When these are present, the installer script must proceed with the installation with no further questions asked.

INSTALLER_ROOT_PASSWORD, e.g., p!wrd&ejwH
INSTALLER_USERNAME, e.g., john
INSTALLER_USER_PASSWORD, e.g., 797jhejwH
INSTALLER_HOSTNAME, e.g., johns-computer
INSTALLER_DEVICE, e.g., da1
INSTALLER_LANGUAGE, e.g., zh
INSTALLER_COUNTRY, e.g., CN
INSTALLER_LOCALE_UTF8, e.g., zh_CN.UTF-8

During installation, the installer script should make liberal use of stdout and stderr. These will not be shown to the user by default but may be helpful for debugging.

The installer script must exit with the exit code 0 on success and may use any other exit codes otherwise. If so desired, we can align on different exit codes that can trigger different reactions in the graphical installer frontend.

Trademarks

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Any individual, organization, or company may, without explicit permission from the Foundation, use the FreeBSD Marks to show support for the Project or as part of a notice to users that a product incorporates the FreeBSD operating system.