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 Note that the kernel accepts a maximum of 8 command line options and 8 environment options (including any options added by default for the installer). If these numbers are exceeded, 2.4 kernels will drop any excess options and 2.6 kernels will panic. With kernel 2.6.9 or newer, you can use 32 command line options and 32 environment options. which may be useful. debconf/priority This parameter sets the lowest priority of messages to be displayed. The default installation uses debconf/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 debconf/priority=medium as boot parameter, you will be shown the installation menu and gain more control over the installation. When debconf/priority=low is used, all messages are shown (this is equivalent to the expert boot method). With debconf/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=slang DEBIAN_FRONTEND=ncurses DEBIAN_FRONTEND=bogl DEBIAN_FRONTEND=gtk DEBIAN_FRONTEND=corba The default front end 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, so this is not very useful right now. 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. 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 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. 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 . preseed/file Specify the path to a preconfiguration file to load to automating the install. See . 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;. rescue/enable Set to true to enter rescue mode rather than performing a normal installation. See .