Boot Manager Shootout: IBM Boot Manager



By: Walter Metcalf
Date: 09/16/98

Introduction

As the conclusion to this loosely-connected series on hard drives, I want to take a look at some of the boot managers available and compare them with each other.

The fundamental purpose of boot managers is to provide support for multiple operating systems on one computer. Regardless of any additional functions they may have, such as security, they must perform that single function well and in an easy to use manner.

I will be examining three boot managers in this three-part article: Boot Manager from IBM, Power Boot from BlueSky Innovations, and System Commander from V Communications.

Review of IBM Boot Manager

As is probably the case with OS/2 users, this was the first boot manager I encountered. First incorporated into OS/2 in v2.0, it very neatly provides the basic functions in a totally integrated fashion. In fact it is so well integrated that it is usually considered simply a feature of OS/2! However for the purposes of this article I am going to treat it as a separate product.

Along the way I will spend some time discussing boot manager architecture in general as a foundation for examining the other two boot managers.

Features

  1. Integrated into OS/2

      All boot managers have two parts: one part runs under an operating system and installs the boot manager code and parameters on to the hard drive. Then second runs this code at the time the computer is booted.

    1. Installation

      1. For those who don't already know, selecting the "Advanced Install" option at the beginning of an OS/2 install procedure automatically enables the installation of Boot Manager.

        • The user is given complete control over what kind and how many partitions he/she wants as well as their size and layout. This is in keeping with OS/2's overall philosophy of user customizability.

      2. Selecting the "Easy Install" automatically precludes the use of the Boot Manager during the installation, although it can be added later.

      Unfortunately this automatic, hidden selection of Boot Manager is sometimes a source of confusion to users new to OS/2 who wish to use Boot Manager but cannot find a place to select or enable it.

    2. FDISK

      1. Boot Manager is set up using extensions to the FDISK and FDISKPM programs. (This is true even during installation, because selecting "Advanced Installation" causes FDISK to be run.) This is logical for two reasons:

        • Boot Manager is installed as a special partition; and
        • All boot managers are intimately involved with the location, type, and number of partitions.

      2. The Boot Manager extension is activated simply by pressing <Enter> on a free space area to install it or on an existing partition to modify its settings, e.g. to add another operating system to the menu. (In FDISKPM the extension is activated by clicking on Options in FDiskPM; see screenshot below.)

      3. I won't present a detailed explanation of how to use FDISK, since that is well-documented in the on-line help and in the OS/2 installation manual. See the IBM Redbooks for additional information.

    3. Partition Magic
        This is not the place to examine Partition Magic in detail. I include it here to note that PowerQuest acquired the right to incorporate IBM's Boot Manager into Partition Magic. (Unfortunately the terms used in Partition Magic are in some cases different from the one's used by Boot Manager in OS/2, introducing still another element of confusion into this already confusing topic.)

  2. Completely compatible with hard disk layout specification.

    1. Boot Manager does not disturb any existing structures on the hard drive (e.g. master boot code). This probably accounts for Boot Manager's remarkable stability and general "harmlessness." I have used Boot Manager heavily since it was introduced in 2.0, often with complex setups, and I do not recall a single case where Boot Manager "bit me" or harmed my data.

    2. Unfortunately this feature has a price: Boot Manager itself requires a primary partition. As we saw in the previous article in this series, the master partition table of a physical drive can hold at most four primary partitions. Owing to the large size of modern hard drives, it's probably safe to say most OS/2 users have at least one logical drive, which means they have an extended partition, which is also a primary partition. (If you find this confusing, I suggest you review the previous article in this series.) If you also have Boot Manager installed, there goes another primary partition, leaving only two. DOS and Windows 9x both require primary partitions, so if you also have both DOS and Windows 9x as I do, you have used all your primary partitions on your system drive. While four doesn't seem like a lot it is usually enough, since OS/2 will install in a logical partition, or on another disk drive, and data partitions almost never require a primary partition. If you look at my partition setup in the FDISKPM screenshot below, you can see I have filled all four primary partitions and have four operating systems. If I were to need another primary partition on that drive, I would need to buy a third-party boot manager. However most non-Microsoft OS do not require primary partitions or need to be installed on the first physical drive. So I could probably install such an OS in a logical partition or a primary partition on my second hard drive. I don't anticipating needing another boot manager any time soon, if ever.

  3. Hidden Drives

    DOS and all varieties of Windows with the possible exception of NT must be installed on the C: drive. (Mr. Gates must think he owns drive C:!) This raises a problem since operating systems do not support two partitions with the same drive letter.

    1. In the screenshot above you'll notice that I have both a straight (MS)DOS partition and a Windows 95 partition installed. Note that only one of them has the drive letter C: beside it. The other one is said to be "hidden," and in fact displays that notation on the Boot Manager menu when my system boots. Either partition may be selected and booted from. If the Win 95 partition is selected, Boot Manager "renames" Win 95 as Drive C: and hides the DOS 6.22 partition. The boot process then continues.
      1. According to the Partition Magic 3.0 manual it is possible to hide logical partitions, but they cannot be booted from.
      2. Partitions may be hidden/unhidden using the FDISK(PM) Options menu, the OS/2 SetBoot program, and several third-party programs including Partition Magic.

        Terminology

        Note: Some of IBM Boot Manager's terminology is different from most of the other programs and literature, so it should be probably be clarified.

    2. Bootable

        The term Bootable as used in the first screen shot has no equivalent in general hard disk specifications. In particular it is in no way equivalent to the term "Active." It simply means that partition is in the Boot Manager menu as displayed when the computer boots. Nothing more and nothing less. The Bootable status is turned on by selecting the option "Add to Boot Manager Menu" in the Options menu below, and turned off by selecting "Remove from Boot Manager Menu."


    3. Startable

        Note that only the Boot Manager partition has the Startable status. "Startable" is exactly equivalent to "Active" as used in nearly all other hard disk literature. Just as there can be only one Active partition there can be only one Startable partition.

        • Note: when a system boots, the master boot code searches for the (only) Startable or Active partition and and loads the boot code in that partition. Boot Manager inserts itself non-invasively into the boot process simply by making itself the Active partition.

          Runs completely under OS/2.

      Although this was mentioned under the OS/2 Compatibility feature, its importance warrants listing by itself.

      Limitations

    4. Requires a primary partition
        This was discussed earlier under "Compatibility with OS/2" and need not be elaborated on here.

    5. No security protection

    6. Limited support for number and variety of operating systems. To some extent this is the result of its complete integration with OS/2 and to some extent it can be viewed as getting what you pay for: after all Boot Manager is free!

      Summary

      IBM's Boot Manager provides at least the basic functions needed by OS/2 users in a very smooth, seamless manner. In addition it is quite well documented both in the online help and the OS/2 manual. In my opinion users should stick with Boot Manager unless they have a definite need for security or a wide variety and/or number of operating systems. Other methods require external DOS programs, are considerably more invasive to the hard drive, and are therefore riskier.

      Next week (yes I am returning to weekly articles!) I will look at two commercially available programs for those whose needs exceed the capabilities of the IBM Boot Manager.

      For further reading:

      Partitions, © 1998 Walter F. Metcalf

      Major Disk Structures and the Boot Process, The PC Guide, © 1997-98 Charles M. Kozierok

      Creating an Optimal Multi-OS Environment with PartitionMagic 3.0, © 1998 (?) PowerQuest Corporation


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