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Installing Debian GNU/Linux 2.1 For Intel x86 - Chapter 6
Booting the Installation System

You have already chosen your boot system in the previous chapter. This could be booting off the Rescue Floppy, booting from CD-ROM, or booting from a pre-installed operating system. This chapter describes some of the ways booting can be controlled, common problems which occur during booting, and some ways to work around them, or at least to help us diagnose the problems.

Note that on some machines, Control-Alt-Delete does not properly reset the machine, so a ``hard'' reboot is recommended. If you are installing from an existing operating system (e.g., from a DOS box) you don't have a choice. Otherwise, please do a hard boot when booting.

6.1 Boot Parameter Arguments

Boot parameters are Linux kernel parameters which are generally used to make sure that peripherals are dealt with properly. For the most part, the kernel can auto-detect information about your peripherals. However, in some cases you'll have to help the kernel a bit.

If you are booting from the Rescue Floppy or from CD-ROM you will be presented with the boot prompt, boot:. Details about how to use boot parameters with the Rescue Floppy can be found in Booting With the Rescue Floppy, Section 6.2. If you are booting from an existing operating system, you'll have to use other means to set boot parameters. You can edit, for instance, the install.bat file with any text editor. Full information on boot parameters can be found in the Linux BootPrompt HOWTO; this section contains only a sketch of the most salient parameters.

If this is the first time you're booting the system, try the default boot parameters (i.e., don't try setting arguments) and see if it works correctly. It probably will. If not, you can reboot later and look for any special parameters that inform the system about your hardware.

When the kernel boots, a message Memory: availk/totalk available should be emitted early in the process. total should match the total amount of RAM, in kilobytes, which is available. If this doesn't match the actual of RAM you have installed, you need to use the mem=ram parameter, where ram is set to the amount of memory, suffixed with ``k'' for kilobytes, or ``m'' for megabytes. For example, both mem=8192k or mem=8m mean 8MB of RAM.

Note that the 2.0 series Linux kernel is limited to 960 MB of memory. If you have more than this amount of RAM in your machine, you'll have to add the boot parameter mem=960m.

Some systems have floppies with ``inverted DCLs''. If you receive errors reading from the floppy, even when you know the floppy is good, try the parameter floppy=thinkpad.

On some systems, such as the IBM PS/1 or ValuePoint (which have ST-506 disk drivers), the IDE drive may not be properly recognized. Again, try it first without the parameters and see if the IDE drive is recognized properly. If not, determine your drive geometry (cylinders, heads, and sectors), and use the parameter hd=cylinders,heads,sectors.

Again, full details on boot parameters can be found in the Linux BootPrompt HOWTO, including tips for obscure hardware. Some common gotchas are included below in Troubleshooting the Boot Process, Section 6.6.

6.2 Booting With the Rescue Floppy

Booting from the Rescue Floppy is easy: place the Rescue Floppy in the primary floppy drive, and reset the system by pressing reset, or by turning the system off and on. As mentioned above, doing a ``hard reboot'' is recommended. The floppy disk should be accessed, and you should then see a screen that introduces the Rescue Floppy and ends with the boot: prompt.

If you are using an alternative way to boot the system, follow the instructions, and wait for the boot: prompt to come up. If you have less than 5MB of memory, you have to boot from the Low-Memory Boot Disk (see Installation on Systems with Low Memory, Section 5.7 below). If you boot from floppies smaller than 1.4MB floppy drive, you have to use a ram-disk boot method, and you will need the Root Disk.

You can do two things at the boot: prompt. You can press the function keys F1 through F10 to view a few pages of helpful information, or you can boot the system.

Information on boot parameters which might be useful can be found by pressing F4 and F5. If you add any parameters to the boot command line, be sure to type the boot method (the default is linux) and a space before the first parameter (e.g., linux floppy=thinkpad). If you simply press Enter, that's the same as typing linux without any special parameters.

The disk is called the Rescue Floppy because you can use it to boot your system and perform repairs if there is ever a problem that makes your hard disk unbootable. Thus, you should save this floppy after you've installed your system. Pressing F3 will give further information on how to use the Rescue Floppy.

Once you press Enter, you should see the message Loading..., and then Uncompressing Linux..., and then a screenful or so of information about the hardware in your system. More information on this phase of the boot process can be found below.

If you choose a non-default boot method, e.g., ``ramdisk'' or ``floppy'', you will be prompted to insert the Root Floppy. Insert the Root Floppy into the first disk drive and press Enter. (If you choose floppy1 insert the Root Floppy into the second disk drive.)

6.3 Booting Low-Memory Systems

If your system has less than 5MB of memory, you should be booting from the Low Memory Boot Floppy as described in Installation on Systems with Low Memory, Section 5.7. The installation system should detect that you don't have enough memory for a normal installation, and ask you to follow a special low-memory installation procedure.

Go through the menu selections in order:

6.4 Booting from CD-ROM

Booting from CD-ROM is simply a question of putting the CD-ROM in the drive and booting. The system should boot up, and you should be presented with the boot: prompt. Here you can enter your boot parameters, and you can select your kernel image.

6.5 Interpreting the Kernel Startup Messages

During the boot sequence, you may see many messages in the form can't find something, or something not present, can't initialize something, or even this driver release depends on something. Most of these messages are harmless. You see them because the kernel for the installation system is built to run on computers with many different peripheral devices. Obviously, no one computer will have every possible peripheral device, so the operating system may emit a few complaints while it looks for peripherals you don't own. You may also see the system pause for a while. This happens when it is waiting for a device to respond, and that device is not present on your system. If you find the time it takes to boot the system unacceptably long, you can create a custom kernel later (see Compiling a New Kernel, Section 8.4).

6.6 Troubleshooting the Boot Process

If you have problems and the kernel hangs during the boot process, doesn't recognize peripherals you actually have, or drives are not recognized properly, the first thing to check is the boot parameters, as discussed in Boot Parameter Arguments, Section 6.1.

Often, problems can be solved by removing add-ons and peripherals, and then trying booting again. Internal modems, sound cards, and Plug-n-Play devices are especially problematic.

The current boot kernel has a known problem with AIC7xxx-based SCSI cards, such as the Adaptec AHA-2940. In some cases, adding the boot arguments aic7xxx=no_probe has worked around the problem. Hopefully, this problem will be fixed soon. Email debian-testing@lists.debian.org if you want to help diagnose and test new kernels to solve this problem.

Tecras and other notebooks, and some non-portables, have a problem where they fail to flush the cache when switching on the A20 gate, which is provoked by bzImage kernels, but not by zImage kernels. If you suffer from this problem, you'll see a message during boot saying A20 gating failed. In this case, you'll have to use the `tecra' boot images, which can be found at Description of Installation System Files, Section 5.2.

If you have errors loading the root filesystem (a RAM-disk image) into memory, such as out of memory errors, you should be booting from the Low Memory Boot Floppy as described in Installation on Systems with Low Memory, Section 5.7. Once you've started booting your low memory system, you should follow the steps outlined in Booting Low-Memory Systems, Section 6.3.

If you have a very old machine, and the kernel hangs after saying Checking 'hlt' instruction..., then you should try the no-hlt boot argument, which disables this test.

If you still have problems, please submit a bug report. Send an email to submit@bugs.debian.org. You must include the following as the first lines of the email:

     Package: boot-floppies
     Version: version

Make sure you fill in version with the version of the boot-floppies set that you used. If you don't know the version, use the date you downloaded the floppies, and include the distribution you got them from (e.g., ``stable'', ``frozen'').

You should also include the following information in your bug report:

     architecture:  i386
     model:         your general hardware vendor and model
     memory:        amount of RAM
     scsi:          SCSI host adapter, if any
     cd-rom:        CD-ROM model and interface type, i.e., ATAPI
     network card:  network interface card, if any
     pcmcia:        details of any PCMCIA devices

Depending on the nature of the bug, it also might be useful to report whether you are installing to IDE or SCSI disks, other peripheral devices such as audio, disk capacity, and the model of video card.

In the bug report, describe what the problem is, including the last visible kernel messages in the event of a kernel hang. Describe the steps that you did which brought the system into the problem state.

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Installing Debian GNU/Linux 2.1 For Intel x86
version 2.1.11, 28 August, 1999
Bruce Perens
Sven Rudolph
Igor Grobman
James Treacy
Adam Di Carlo