Red Hat Enterprise Linux 4: Installation Guide for x86, Itanium™, AMD64, and Intel® Extended Memory 64 Technology (Intel® EM64T)
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# Appendix F. Additional Boot Options

This appendix discusses additional boot and kernel boot options available for the Red Hat Enterprise Linux installation program.

To use any of the boot options presented here, type the command you wish to invoke at the installation `boot:` prompt.

Boot Time Command Arguments

`askmethod`

  This command asks you to select the installation method you would like to use when booting from the Red Hat Enterprise Linux CD-ROM.

`apic`

  This x86 boot command works around a bug commonly encountered in the Intel 440GX chipset BIOS and should only be executed with the installation program kernel.

`apm=allow_ints`

  This x86 boot command changes how the suspend service is handled (and may be necessary for some laptops).

`apm=off`

  This x86 boot command disables APM (Advanced Power Management). It useful because some BIOSes have buggy power management (APM) and tend to crash.

`apm=power_off`

  This x86 boot command makes Red Hat Enterprise Linux shutdown (power off) the system by default. It is useful for SMP systems that do not shutdown by default.

`apm=realmode_power_off`

  Some BIOSes crash on x86-based systems when trying to shutdown (power off) the machine. This command changes the method of how this is done from the Windows NT way to the Windows 95 way.

`dd`

  This argument causes the installation program to prompt you to use a driver diskette.

`dd=url`

  This argument causes the installation program to prompt you to use a driver image from a specified HTTP, FTP, or NFS network address.

`display=IP:0`

  This command allows remote display forwarding. In this command, IP should be replaced with the IP address of the system on which you want the display to appear.

  On the system you want the display to appear on, you must execute the command `xhost +remotehostname`, where remotehostname is the name of the host from which you are running the original display. Using the command `xhost +remotehostname` limits access to the remote display terminal and does not allow access from anyone or any system not specifically authorized for remote access.

`driverdisk`

  This command performs the same function as the `dd` command and also prompts you to use a driver diskette during the installation of Red Hat Enterprise Linux.

`ide=nodma`

  This command disables DMA on all IDE devices and may be useful when having IDE-related problems.

`linux upgradeany`

  This command relaxes some of the checks on your `/etc/redhat-release` file. If your `/etc/redhat-release` file has been changed from the default, your Red Hat Enterprise Linux installation may not be found when attempting an upgrade to Red Hat Enterprise Linux 4. Use this option only if your existing Red Hat Enterprise Linux installation was not detected.

`mediacheck`

  This command gives you the option of testing the integrity of the install source (if an ISO-based method). This command works with the CD, DVD, hard drive ISO, and NFS ISO installation methods. Verifying that the ISO images are intact before you attempt an installation helps to avoid problems that are often encountered during an installation.

`mem=xxxM`

  This command allows you to override the amount of memory the kernel detects for the machine. This may be needed for some older systems where only 16 MB is detected and for some new machines where the video card shares the video memory with the main memory. When executing this command, xxx should be replaced with the amount of memory in megabytes.

`nmi_watchdog=1`

  This command enables the built-in kernel deadlock detector. This command can be used to debug hard kernel lockups. By executing periodic NMI (Non Maskable Interrupt) interrupts, the kernel can monitor whether any CPU has locked up and print out debugging messages as needed.

`noapic`

  This x86 boot command tells the kernel not to use the APIC chip. It may be helpful for some motherboards with a bad APIC (such as the Abit BP6) or with a buggy BIOS. Systems based on the NVIDIA nForce3 chipset (such as the ASUS SK8N) have been known to hang during IDE detection at boot time, or display other interrupt-delivery issues.

`noht`

  This x86 boot command disables hyperthreading.

`nofb`

  This command disables frame buffer support and allows the installation program to run in text mode. This command may be necessary for accessibility with some screen reading hardware.

`nomce`

  This x86 boot command disables self-diagnosis checks performed on the CPU. The kernel enables self-diagnosis on the CPU by default (called Machine Check Exception). Early Compaq Pentium systems may need this option as they do not support processor error checking correctly. A few other laptops, notably those using the Radeon IGP chipset, may also need this option.

`nopass`

  This command disables the passing of keyboard and mouse information to stage 2 of the installation program. It can be used to test keyboard and mouse configuration screens during stage 2 of the installation program when performing a network installation.

`nopcmcia`

  This command ignores any PCMCIA controllers in system.

`noprobe`

  This command disables hardware detection and instead prompts the user for hardware information.

`noshell`

  This command disables shell access on virtual console 2 during an installation.

`nousb`

  This command disables the loading of USB support during the installation. If the installation program tends to hang early in the process, this command may be helpful.

`nousbstorage`

  This command disables the loading of the usbstorage module in the installation program's loader. It may help with device ordering on SCSI systems.

`numa=off`

  Red Hat Enterprise Linux supports NUMA (Non-Uniform Memory Access) on the AMD64 architecture. While all CPUs can access all memory even without NUMA support, the NUMA support present in the updated kernel causes memory allocations to favor the CPU on which they originate as much as possible, thereby minimizing inter-CPU memory traffic. This can provide significant performance improvements in certain applications. To revert to the original non-NUMA behavior, specify this boot option.

`reboot=b`

  This x86, AMD64, and Intel® EM64T boot command changes the way the kernel tries to reboot the machine. If a kernel hang is experienced while the system is shutting down, this command may cause the system to reboot successfully.

`rescue`

  This command runs rescue mode. Refer to the Red Hat Enterprise Linux System Administration Guide for more information about rescue mode.

`resolution=`

  Tells the installation program which video mode to run. It accepts any standard resolution, such as `640x480`, `800x600`, `1024x768`, and so on.

`serial`

  This command turns on serial console support.

`skipddc`

  This x86 boot command skips the `ddc` monitor probe which causes problems on some systems.

`text`

  This command disables the graphical installation program and forces the installation program to run in text mode.

`updates`

  This command prompts you to insert a floppy diskette containing updates (bug fixes). It is not needed if you are performing a network installation and have already placed the updates image contents in `RHupdates/` on the server.

`vnc`

  This command allows you to install from a VNC server.

`vncpassword=`

  This command sets the password used to connect to the VNC server.

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