Deciphering BOOT.INI
Serdar Yegulalp

The BOOT.INI file is a hidden file kept in the root directory of your Windows 2000 boot drive. It holds the path names and drive information for where your system files are being kept. If your system is damaged, or if you want to create a boot floppy to bring your system back up, you will need to know how BOOT.INI works.

A basic BOOT.INI file looks like this:

[boot loader]

timeout=30

default=multi(0)disk(0)rdisk(0)partition(1)WINNT

[operating systems]

multi(0)disk(0)rdisk(0)partition(1)WINNT="Microsoft Windows 2000 Server" /fastdetect

The ARC (or Advanced RISC Computing) path specifications used in BOOT.INI to describe where files are held can be incredibly arcane. If you use an IDE or EIDE-type controller, the BOOT.INI file entries look like this:

    multi(x)disk(x)rdisk(x)partition(x)<systemdirectory>

MULTI() indicates that the controller being used works through the system's BIOS via INT 13. Usually this is set to 0, because BIOS can generally only identify a single INT 13 controller at a time.

DISK() is also set to 0 when using MULTI(), again because the disk information is provided through INT 13 and doesn't need to be enumerated.

RDISK() is the ordinal number of the disk on the adapter. With EIDE controllers, this is a number from 0 to 3, with the primary boot

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drive being 0

PARTITION() is the number of the partition on the drive. This starts at 1, not 0, and all partitions save for MS-DOS extended partitions and unused partitions get a number. If you add or remove partitions in the Windows 2000 Disk Management console, you will get a warning that you manually need to edit this number before you reboot the system.

With machines that use a SCSI controller to hold the system disk, the syntax is:

    scsi(x)disk(x)rdisk(x)partition(x)<systemdirectory>

SCSI() is the number of the adapter. If your SCSI adapter uses INT 13 and does not require its own driver to boot (which is a copy of the SCSI driver for the controller, copied into the root directory and renamed to NTBOOTDD.SYS), then you use the MULTI() syntax, not SCSI(). If you have multiple adapters in a system, the numbering will conform to the order in which they are recognized by BIOS.

DISK() is the SCSI ID of the target disk.

RDISK() is the SCSI logical unit number (or LUN), which is almost always 0.

PARTITION() is the partition number, which follows the same numbering convention as MULTI()'s PARTITION() numbering.

In both MULTI() and SCSI(), the final parameter is the actual pathname to the system files, which is usually WINNT.


Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter.


This was first published in December 2001

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