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June 13, 2001 12:00 AM

Kick-Start Startup with Boot.ini

Windows IT Pro
InstantDoc ID #21192
Rating: (1)
This little file has big possibilities

After you install Windows 2000, a small, hidden, read-only text file—boot.ini—exists in the boot partition's root directory. This file is an important component in the machinery that controls the OS startup processes. The installation process creates the file's contents, so boot.ini is specific to the computer. Understanding boot.ini's format, its likely content, the conventions that its content follows, and your options for manipulating the file gives you two important elements of control over a system. First, you can change the file's contents to modify the startup process. Second, you can create a boot.ini file to repair a computer that won't boot.

You can edit boot.ini in any text editor. Before you do so, I suggest you copy the original file to a 3.5" disk in case your changes wreak havoc. Boot.ini is read-only, so you must change that attribute before you can save your edits. (Of course, don't forget to restore the read-only attribute when you've finished editing.)

Content: Boot.ini's Sections
All .ini files follow the same format rules. The contents are arranged in sections, and each section has a title enclosed in square brackets. As Figure 1, page 110, shows, boot.ini has two sections: [boot loader] and [operating systems].

The [boot loader] section contains a timeout specification and a pointer to the default OS's location. The timeout specification is the amount of time, in seconds, during which users can make a selection from the onscreen menu that appears when users have a choice of startup options. By default, the timeout duration is 30 seconds, and the default OS loads if users fail to make a choice within that time.

Typically, a choice of startup options occurs when more than one OS exists on the system (e.g., you updated a previous OS to Win2K and kept the previous OS, you installed two versions of Windows).

A choice also exists when you've installed the Recovery Console (RC), which automatically adds the Microsoft Windows 2000 Recovery Console option to the onscreen menu. (The RC is an advanced feature that you can use to repair a broken installation. For information about this feature, see Sean Daily, "Mastering the Recovery Console," July 2000.)

When users have no choices, no onscreen menu appears. The system ignores the timeout specification and immediately begins the OS startup.

Boot.ini's [operating systems] section contains the path or paths to the OS or OSs on the computer. As Figure 1 shows, text strings enclosed in quotation marks represent the text lines that the onscreen menu displays. You can edit the onscreen text to provide special instructions. For example, if you install a beta version of the next Windows version, you can edit the text to say Not for production.

Conventions: ARC Path Statements
The [boot loader] section's OS location information and the [operating systems] section's OS path information both follow the conventions in the Advanced RISC Computing (ARC) specifications. Win2K recognizes three ARC path structures: multi syntax, SCSI syntax, and signature syntax.

Multi syntax. Systems that utilize IDE hard disks commonly use the multi syntax in boot.ini. Using the multi syntax tells Win2K to depend on the computer BIOS to load the system files. The OS uses INT 13 BIOS calls to find the disk that holds ntoskrnl.exe and the other files the system needs to boot the OS. You can also use the multi syntax for SCSI drives if the SCSI device is configured to use INT 13 calls instead of the device's BIOS settings.

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Comments
  • Anonymous User
    8 years ago
    Oct 31, 2004

    very good and informative, helped me fix a dual boot issue

  • Kevin
    8 years ago
    Jun 04, 2004

    Article is well written & very informative. But I'd like to ask a question to clarify something. In the line: "In a multi syntax line,... ... C is an ordinal number that specifies the disk attached to the adapter; the number can range from 0 to 3, depending on the number of drives on the adapter." Does the value indicate the quantity of drives in the system, or their hierarchy? For example, if I mirror my
    boot drive in Windows 2000, it tells me to edit my boot.ini file if I want to boot from the 2nd drive in the mirror (if
    the initial boot drive died, for example.) Can I edit it so it would automatically look/accept for the O/S on the 2nd drive (after removing dead 1st drive) by adding 2 in the rdisk entry, or only after the fact by editing the value to
    1 (or whatever)? In short, can the boot.ini file be written in such a way to make the system bootable from either Disk0 or Disk1 at will? Would a typical boot.ini work like this:

    [boot loader]
    timeout=30
    default=multi(0)disk(0)rdisk(2)partition(2)\\WINNT
    [operating systems]
    multi(0)disk(0)rdisk(2)partition(2)\\WINNT="Microsoft Windows 2000 Server" /fastdetect

    Appreciate any insight/clarification you can provide. Thanks

  • Steve
    8 years ago
    Jan 25, 2004

    More informative.Good work.

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