Kernel parameters

Some aspects of the Linux kernels behaviour are controllable via so called kernel parameters. These are parameters similar to the ones that you would provide for a command like $ ls or $ cp in a shell, only that they are appended to the kernel/image line in your bootmanagers config file (for lilo this would typically be /etc/lilo.conf, for grub it would be /boot/grub/menu.lst).

An example line from grub could look like this:

kernel /lfskernel-2.6.9 root=/dev/hda6 rw idebus=66 vga=791 splash=silent acpi_sleep=s3_bios

For a complete overview of all available parameters see /lib/modules/`uname -r`/source/Documentation/kernel-parameters.txt.

Typical parameters used on ThinkPads

The following table gives an overview of the kernel parameters typically needed on ThinkPads.

useful kernel parameters

parameter	description
acpi=off	disables ACPI (keeps it from overriding APM)
acpi_sleep=s3_bios	makes the system call the video BIOS to reenable video on resume from suspend-to-ram (use this if you experience a blank display after resume while your system seems elsewise awake)
hda=noprobe	Sometimes needed for DMA support for system hard disk on recent models (see Problems with SATA and Linux)
hdc=noprobe libata.atapi_enabled=1	Sometimes needed for DMA support for the optical drive on recent models (see Problems with SATA and Linux)
idebus=66	set IDE bus speed to 66 MHz (66 is maximum supported)
nolapic	tells the kernel not to use the local APIC (use if you have problems with ACPI)
lapic	tells the kernel to use the local APIC, even when it is disabled by the BIOS (older models like a T42 or R51 don't have this option in the BIOS and don't enable the local APIC)
noresume noresume2	boots without resuming after a suspend-to-disk (for swsusp and suspend2, respectively)
resume=/dev/hdaX resume2=/dev/hdaX	tells the kernel where to find the suspend-to-disk image to resume from (for swsusp and suspend2, respectively)
root=/dev/hdaX	tells the kernel where to find the root filesystem
speedstep_coppermine=???	supposed to tell the kernel that you have a speedstep capable coppermine processor, but could possibly not work anymore with newer kernels
forcepae	tells the kernel that the CPU supports Physical Address Extension (PAE), even if it is not the list of supported CPU flags (see Intel Pentium M (Dothan))

Framebuffer related parameters for ThinkPads

The following table gives an overview of the kernel parameters typically needed on ThinkPads.

useful framebuffer related kernel parameters

parameter	description
vga=835	for 1400x1050 framebuffer resolution
vga=0x33c	same as above
video=vesa:ywrap,mtrr	enables mtrr and ....
video=radeonfb:vesa:1400x1050-32@60	for using accelerated radeonfb framebuffer