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 this is the first time you're booting the system, try the default boot parameters (i.e., don't try setting parameters) 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. Information on many boot parameters can be found in the Linux BootPrompt HOWTO, including tips for obscure hardware. This section contains only a sketch of the most salient parameters. Some common gotchas are included below in . 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. If this doesn't match the actual amount 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=65536k and mem=64m mean 64MB of RAM. If you are booting with a serial console, generally the kernel will autodetect this (although not on DECstations). 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. For &arch-title; the serial devices are ttya or ttyb. Alternatively, set the input-device and output-device OpenPROM variables to ttya. The installation system recognizes a few additional boot parameters With current kernels (2.6.9 or newer) you can use 32 command line options and 32 environment options. If these numbers are exceeded, the kernel will panic. which may be useful. debconf/priority This parameter sets the lowest priority of messages to be displayed. Short form: priority The default installation uses priority=high. This means that both high and critical priority messages are shown, but medium and low priority messages are skipped. If problems are encountered, the installer adjusts the priority as needed. If you add priority=medium as boot parameter, you will be shown the installation menu and gain more control over the installation. When priority=low is used, all messages are shown (this is equivalent to the expert boot method). With priority=critical, the installation system will display only critical messages and try to do the right thing without fuss. DEBIAN_FRONTEND This boot parameter controls the type of user interface used for the installer. The current possible parameter settings are: DEBIAN_FRONTEND=noninteractive DEBIAN_FRONTEND=text DEBIAN_FRONTEND=newt DEBIAN_FRONTEND=gtk The default frontend is DEBIAN_FRONTEND=newt. DEBIAN_FRONTEND=text may be preferable for serial console installs. Generally only the newt frontend is available on default install media. On architectures which support it, the graphical installer uses the gtk frontend. BOOT_DEBUG Setting this boot parameter to 2 will cause the installer's boot process to be verbosely logged. Setting it to 3 makes debug shells available at strategic points in the boot process. (Exit the shells to continue the boot process.) BOOT_DEBUG=0 This is the default. BOOT_DEBUG=1 More verbose than usual. BOOT_DEBUG=2 Lots of debugging information. BOOT_DEBUG=3 Shells are run at various points in the boot process to allow detailed debugging. Exit the shell to continue the boot. INSTALL_MEDIA_DEV The value of the parameter is the path to the device to load the Debian installer from. For example, INSTALL_MEDIA_DEV=/dev/floppy/0 The boot floppy, which normally scans all floppies it can to find the root floppy, can be overridden by this parameter to only look at the one device. debian-installer/framebuffer Some architectures use the kernel framebuffer to offer installation in a number of languages. If framebuffer causes a problem on your system you can disable the feature by the parameter debian-installer/framebuffer=false, or fb=false for short. Problem symptoms are error messages about bterm or bogl, a blank screen, or a freeze within a few minutes after starting the install. The video=vga16:off argument may also be used to disable the kernel's use of the framebuffer. Such problems have been reported on a Dell Inspiron with Mobile Radeon card. Such problems have been reported on the Amiga 1200 and SE/30. Such problems have been reported on hppa. Because of display problems on some systems, framebuffer support is disabled by default for &arch-title;. This can result in ugly display on systems that do properly support the framebuffer, like those with ATI graphical cards. If you see display problems in the installer, you can try booting with parameter debian-installer/framebuffer=true or fb=true for short. debian-installer/theme A theme determines how the user interface of the installer looks (colors, icons, etc.). What themes are available differs per frontend. Currently both the newt and gtk frontends only have a dark theme that was designed for visually impaired users. Set the theme by booting with parameter debian-installer/theme=dark or theme=dark. debian-installer/probe/usb Set to false to prevent probing for USB on boot, if that causes problems. netcfg/disable_dhcp By default, the &d-i; automatically probes for network configuration via DHCP. If the probe succeeds, you won't have a chance to review and change the obtained settings. You can get to the manual network setup only in case the DHCP probe fails. If you have a DHCP server on your local network, but want to avoid it because e.g. it gives wrong answers, you can use the parameter netcfg/disable_dhcp=true to prevent configuring the network with DHCP and to enter the information manually. hw-detect/start_pcmcia Set to false to prevent starting PCMCIA services, if that causes problems. Some laptops are well known for this misbehavior. preseed/url Specify the url to a preconfiguration file to download and use in automating the install. See . Short form: url. preseed/file Specify the path to a preconfiguration file to load to automating the install. See . Short form: file. auto-install/enabled Delay questions that are normally asked before preseeding is possible until after the network is configured. Short form: auto=true See for details about using this to automate installs. cdrom-detect/eject By default, before rebooting, &d-i; automatically ejects the optical media used during the installation. This can be unnecessary if the system does not automatically boot off the CD. In some cases it may even be undesirable, for example if the optical drive cannot reinsert the media itself and the user is not there to do it manually. Many slot loading, slim-line, and caddy style drives cannot reload media automatically. Set to false to disable automatic ejection, and be aware that you may need to ensure that the system does not automatically boot from the optical drive after the initial installation. ramdisk_size If you are using a 2.2.x kernel, you may need to set &ramdisksize;. mouse/left For the gtk frontend (graphical installer), users can switch the mouse to left-handed operation by setting this parameter to true. directfb/hw-accel For the gtk frontend (graphical installer), hardware acceleration in directfb is disabled by default. To enable it, set this parameter to true when booting the installer. rescue/enable Set to true to enter rescue mode rather than performing a normal installation. See . With some exceptions, a value can be set at the boot prompt for any question asked during the installation, though this is only really useful in specific cases. General instructions how to do this can be found in . Some specific examples are listed below. debian-installer/locale Can be used to set both the language and country for the installation. This will only work if the locale is supported in Debian. Short form: locale. For example, use locale=de_CH to select German as language and Switserland as country. netcfg/disable_dhcp Set to true if you want to disable DHCP and instead force static network configuration. tasksel:tasksel/first Can be used to select tasks that are not available from the interactive task list, such as the kde-desktop task. See for additional information. Short form: tasks. If drivers are compiled into the kernel, you can pass parameters to them as described in the kernel documentation. However, if drivers are compiled as modules and because kernel modules are loaded a bit differently during an installation than when booting an installed system, it is not possible to pass parameters to modules as you would normally do. Instead, you need to use a special syntax recognized by the installer which will then make sure that the parameters are saved in the proper configuration files and will thus be used when the modules are actually loaded. The parameters will also be propagated automatically to the configuration for the installed system. Note that it is now quite rare that parameters need to be passed to modules. In most cases the kernel will be able to probe the hardware present in a system and set good defaults that way. However, in some situations it may still be needed to set parameters manually. The syntax to use to set parameters for modules is: module_name.parameter_name=value If you need to pass multiple parameters to the same or different modules, just repeat this. For example, to set an old 3Com network interface card to use the BNC (coax) connector and IRQ 10, you would pass: 3c509.xcvr=3 3c509.irq=10