MS-DOS 6.22 Setup Installation Log Utility

During the installation of MS-DOS 6.22, the primary utility responsible for creating an installation log is the setup program itself, SETUP.EXE. This article explains how SETUP.EXE generates the installation log file named SETUP.LOG, where the log is stored, what data it tracks, and how it functions alongside the uninstallation and rollback process.

The Role of SETUP.EXE

When you boot from the setup diskettes or run the installer from a floppy drive, MS-DOS launches SETUP.EXE. This executable guides the user through partitioning, formatting, and copying operating system files to the target drive. During this procedure, SETUP.EXE automatically tracks every modification made to the host machine to ensure that the installation can either be verified or completely reversed if an error occurs.

Generation of SETUP.LOG

The log file produced by the utility is named SETUP.LOG. Rather than leaving this file on the target hard drive during a standard upgrade, SETUP.EXE writes SETUP.LOG directly to the Uninstall Disk (or Disks) created during the setup routine.

The creation process involves the following steps:

  1. System Inspection: SETUP.EXE checks the machine's hardware, existing DOS version, and file system structure.
  2. Uninstall Disk Creation: The utility prompts the user to insert one or two blank floppy disks labeled "Uninstall."
  3. Log Writing: As files are transferred, SETUP.EXE writes sector allocations, directory modifications, and a record of every replaced file into SETUP.LOG on the Uninstall disk.

Contents of SETUP.LOG

The SETUP.LOG file is a plain text and data mapping record containing:

  • The original location of critical boot sectors (Master Boot Record and Partition Boot Record).
  • Pointers and cluster locations for existing system files, such as IO.SYS, MSDOS.SYS, and COMMAND.COM.
  • A manifest of all new files copied to the DOS directory.
  • Information regarding the previous operating system version to facilitate a clean rollback.

Utilizing the Log with UNINSTAL.EXE

The generated SETUP.LOG works directly with the UNINSTAL.EXE utility located on the Uninstall disk. If the user decides to revert to their previous DOS version, or if setup fails midway through copying system files, booting from the Uninstall disk triggers UNINSTAL.EXE. This program reads SETUP.LOG to restore the original boot records, move replaced files back to their original sectors, and remove the newly installed MS-DOS 6.22 binaries.

If an administrator runs SETUP /Q to perform a quick installation without creating uninstall disks, the generation of the uninstall-linked SETUP.LOG is bypassed.