You have already chosen your boot system in the previous chapter. This could be booting off the Rescue Floppy, booting from CD-ROM, booting from the network, 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.
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.
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.
If you are booting with a serial console, generally the kernel will autodetect this. If you have a videocard (framebuffer) and a keyboard also attached to the computer which you wish to boot via serial console, you may have to pass the console=device argument to the kernel, where device is your serial device, which is usually something like ``ttyS0''.
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 6.5.
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. 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 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.)
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.
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).
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.
If you still have problems, please submit a bug report. Send an email
firstname.lastname@example.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: m68k 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.