freebsd-dev/share/FAQ/TROUBLESHOOTING

Troubleshooting Tips - or "These are the times that try men's souls"
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The following tips and tricks may help you turn a failing (or failed)
installation attempt into a success.  Please read them carefully.

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Summary:	Hardware conflict or misconfiguration.

Problem:	A device is conflicting with another or doesn't match
		the kernel's compiled-in IRQ or address.

Cause:		While most device drivers in FreeBSD are now smart
		enough to match themselves to your hardware settings
		dynamically, there are a few that still require fairly
		rigid configuration parameters to be compiled in (and
		matched by the hardware) before they'll work.  We're
		working hard to eliminate as many of these last
		hold-outs as we can, but it's not always as easy as
		it looks.

Solution:	There are several possible solutions.  The first,
		and easiest, is to boot the kernel with the -c flag.
		When you see the initial boot prompt (from floppy or
		hard disk), type:

			/kernel -c

		This will boot just past the memory sizing code and
		then drop into a dynamic kernel configuration utility.
		Type `?' at the prompt to see a list of commands.  You
		can use this utility to reset the IRQ, memory address,
		IO address or a number of other device configuration
		parameters.  You can also disable a device entirely
		if it's causing problems for other devices you'd much
		rather have work.  Note that this only affects the
		kernel being booted temporarily, it does not "write out"
		the information to the kernel so that these settings
		are permanantly altered (this would be actually rather
		hard).  If you reboot, you'll have to make the same
		changes again.  The goal of the -c utility is to get
		you up far enough to be able to download the appropriate
		sources and configure and rebuild a kernel more specific
		to your needs.

		Another solution is, obviously, to remove the offending
		hardware or simply strip the system down to the bare
		essentials until the problem (hopefully) goes away.
		Once you're up, you can do the same thing mentioned
		above - compile a kernel more suited to your hardware,
		or incrementally try to figure out what it was about
		your original hardware configuration that didn't work.

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Summary:	Newfs crashes, requesting that blocksize be 32K

Cause:		You have your SCSI controller configured to translate
		geometries for disks >1GB in size.

Solution:	Turn such translation OFF in your controller's BIOS
		setup!  FreeBSD has no problems with disks >1GB just
		so long as the root partition starts and ends BELOW
		cylinder 1024.  This is a PC hardware limitation.
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Summary:	FreeBSD won't boot off the hard disk

Cause:		Root partition does not start and end below cylinder 1024.

Solution:	See solution for newfs crashes, or move your root
		partition.  This limitation holds true for ANY operating
		system you wish to boot from your hard drive.

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Summary:	FreeBSD still won't boot off the hard disk

Cause:		No boot code is installed in sector 1.

Solution:	Chose the Write MBR (B)oot code in the FDISK editor.

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Summary:	Nope, FreeBSD's still not booting from the hard disk.

Cause:		BIOS disk geometry different from that used when
		installing FreeBSD.

Solution:	With IDE drives, pay careful attention to the geometry
		information that FreeBSD prints out when it's first
		booting off the floppy.  Use this geometry in your BIOS
		setup or use the BIOS geometry when you install FreeBSD.
		Either way, they have to match.

		With SCSI drives, the values they report is most often
		bogus and cannot be used.  In this situation, the SCSI
		controller is performing geometry translation and
		it's probably wise to assume a default of 64 heads,
		32 sectors and 1MB/cylinder.  Use these values when
		you install FreeBSD.  See above comments concerning
		newfs failures for more info.