UbuntuHelp:BootOptions
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Boot Options
When and How to Use
There are at least major two cases where one may wish to use boot options.
Case 1: When trying to install, and the install freezes.
Case 2: After a system has been installed and does not boot or the system needs adjustment.
When installing
When your installer/live CD loads you will come to this page:
Go ahead and hit the F6 key.
After you hit F6 you will see a screen that looks like this:
Simply append the options you want to the end of the line. This will mean that you get to turn off or alter the way the machine boots. Here is an example of adding an option:
For Installed Systems That Need Adjustment
This will explain how to edit the grub menu entries on the fly (not permanently).
This assumes of course that have installed grub, the default boot loader in Ubuntu. (This article does not deal with alternatives like lilo.)
As the machine starts to boot you get a Grub message, at this time press the ESC key. This drops you to a text menu. Choose the boot option you want to work with. Navigate using the the up and down arrow keys. (Cursor key.)
When you have selected the menu item press 'e'.
Then you will be presented with a "root" line on the first line. You must then move to the "kernel" line one down from there with the down arrow. then again you press 'e'.
Go to the end of the line (ctrl-E) and add the command from below.
Press the enter key when you are done with the changes, and finally press 'b' to boot.
Your machine will now hopefully boot.
Options for the boot command line.
This list is not comprehensive but it contains some of the common options. When presented with the text on the screen "boot:" then the options below can be given. They must have the kernel name before the option.
Example: Adding the vga=771 option
boot: /boot/vmlinuz-2.6.15-26-k7 root=/dev/hda1 ro quiet splash
boot: /boot/vmlinuz-2.6.15-26-k7 root=/dev/hda1 ro quiet splash vga=771
Options can be used together such as in this example:
/boot/vmlinuz-2.6.15-26-k7 root=/dev/hda1 ro quiet splash noapic nolapic
Kernel Options
These options are used by the kernel, and will apply to any system at any time.
Option: vga=771
Impact: Helps where there are problems with laptop screens. NB! 771 is one possibility that works with some screens. Other screens need another number.
Option: noacpi
Impact: Does not start the Advanced Configuration and Power Interface (ACPI). Can prevent the impact of bad ACPI implementations, which in turn cause random reboots or system lockups.
Option: noapic nolapic
Impact: A broken "Advanced Programmable Interrupt Controller" may work with this option. They usually randomly freeze machines or produce repetitive messages about IRQ issues. nolapic means "no local apic".
Installer options (user-land)
These options are usually used when installing a system, and are picked up by the installer program or start-up scripts, and not by the kernel.
Option: debian-installer/framebuffer=false
Impact: Disable framebuffer.
Option: hw-detect/start_pcmcia=false
Impact: Don't start PCMCIA. Personal Computer Memory Card International Association, one of the stranger names for a piece of hardware. :-) Your hardware is an association.
Option: netcfg/disable_dhcp=true
Impact: Force static network config.
Option: bootkbd=uk
Impact: Set keyboard map. Use a two letter ISO country code to get the right letters on the right keys. This option can help with password problems.
(This list is far from complete, please feel free to add some options.)
Permanent changes
Once you know you need to boot with a special option on your installed system, you'll have to edit the file /boot/grub/menu.lst to make the boot option permanent.
To to this please do the following:
sudo nano /boot/grub/menu.lst
Add the option to the line that starts with "# kopt=". Then run
sudo update-grub
to have the menu entries updated.
NB! If you instead edit the menu entries directly, your changes will magically disappear the next time update-grub
is run, for instance when system packages are updated.