Kernel parameters

2004-12-14T19:08:15Z

217.230.163.254: page created

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 wouuld 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 <code>/lib/modules/`uname -r`/source/Documentation/kernel-parameters.txt</code>.

==Typical parameters used on ThinkPads==
The following table gives an overview of the kernel parameters typically needed on ThinkPads.
{| border="1" cellspacing="0" cellpadding="2"
|+ 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)
|-
| 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)
|-
| noresume || boots without resuming after a suspend-to-disk
|-
| resume=/dev/hdaX || tells the kernel where to find the suspend-to-disk image to resume from
|-
| 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 kenrels
|-
|}

How to make APM work

2004-12-14T17:33:47Z

217.230.163.254: cosmetics, added ACPI override comment

===general===
You need to enable the APM Power Management support in the kernel and install the [[apmd]] to handle the events triggered by the kernel driver.
The configuration for what to do at the different events is done in the proxy script which is usually found in <code>/etc/apmd_proxy</code>.
See <tt>man apmd</tt> for further information on this.

If both ACPI and APM are enabled in your kernel, ACPI will override APM on boot if an ACPI capable BIOS is detected. To keep it from doing so add <code>acpi=off</code> to your [[kernel parameters]].

===Screen blanking (Standby)===
apm -S will standby the machine. Fn+F3 should result in the same thing.

===Suspend to RAM (Sleep)===
apm -s will suspend the machine. Fn+F4 should do the same thing.

===Suspend to disk (Hibernate)===
The Phoenix BIOS allows you three ways to hibernate with APM:
*using a special partition
*using a hibernation file on a dos type partition
*using [http://developer.berlios.de/projects/softwaresuspend/ SoftwareSuspend2]

====using a hibernation partition====
The partition to be used for hibernation must be a primary partition that is at least as big as your laptop's memory including its video ram. First set the partition type of this partition to a0 (IBM Thinkpad hibernation) with fdisk, and then use [[tphdisk]] to write a hibernation file directly to this partition.

Only follow these instructions, if you understand them. You will overwrite a partition on your hard disk and might loose valuable data - consider yourself warned. For example, assume that /dev/hda2 is the partition that is to be converted to a hibernation partition. Become root and type '''/sbin/fdisk /dev/hda'''. At the fdisk prompt type '''t''' to change the partition type, then type '''2''' to indicate that you want to change the type of partition 2, and then enter the partition type: '''a0'''. Now type '''w''' to write the partition table back to disk and exit. After that use [[tphdisk]] to initialize the hibernation partition. First estimate the size of your laptop's memory (main and video). For the sake of this example, let us assume that the main memory is 1024 MB and the video card has 128 MB of memory. Then the command '''tphdisk 1152 > /dev/hda2''' will initialize the hibernation partition. Note that this will only work if the partition is big enough. After a reboot, Fn+F12 will work as expected.

I have successfully used this method on a T41 (2373GEU) that runs Fedora Core 3.

====using a hibernation file on a dos partition====
The partition to put the file on must be a dos or vfat partition. Fat32 formatted partitions have been reported successful as well as Fat16 formatted ones. The file is either created with phdisk.exe, if you happen to have a floppy drive and a bootable dos floppy disk that you can start it from.
Under Linux [[tphdisk]] will do this job for you.

There have been varying reports of success or lack thereof using [[tphdisk]]; see [[APM setup on a type 2379 Thinkpad T40]] for workarounds if [[tphdisk]] doesn't do the trick.

====using SoftwareSuspend2====
ToDo...

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Kernel parameters

How to make APM work