kexec man page on Knoppix

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kexec(8)			 User Manuals			      kexec(8)

NAME
       kexec - directly boot into a new kernel

SYNOPSIS
       /sbin/kexec  [-v	 (--version)]  [-f  (--force)]	[-x (--no-ifdown)] [-l
       (--load)]  [-p  (--load-panic)]	[-u  (--unload)]  [-e  (--exec)]   [-t
       (--type)] [--mem-min=addr] [--mem-max=addr]

DESCRIPTION
       kexec  is  a system call that enables you to load and boot into another
       kernel from the currently running kernel.  kexec performs the  function
       of  the	boot  loader  from  within  the kernel. The primary difference
       between a standard system boot and a kexec boot is  that	 the  hardware
       initialization normally performed by the BIOS or firmware (depending on
       architecture) is not performed during a kexec boot. This has the effect
       of reducing the time required for a reboot.

       Make sure you have selected CONFIG_KEXEC=y when configuring the kernel.
       The CONFIG_KEXEC option enables the kexec system call.

USAGE
       Using kexec consists of

	      (1) loading the kernel to be rebooted to into memory, and
	      (2) actually rebooting to the pre-loaded kernel.

       To load a kernel, the syntax is as follows:

	      kexec   -l kernel-image	--append=command-line-options	--ini‐
	      trd=initrd-image

       where kernel-image is the kernel file that you intend to reboot to.

       Insert  the command-line parameters that must be passed to the new ker‐
       nel  into  command-line-options.	  Passing  the	 exact	 contents   of
       /proc/cmdline  into  command-line-options  is  the safest way to ensure
       that correct values are passed to the rebooting kernel.

       The optional initrd-image is the initrd image to be used during boot.

       It's also possible to invoke kexec without an option parameter. In that
       case,  kexec  loads  the specified kernel and then invokes shutdown(8).
       If the shutdown scripts of your Linux distribution support  kexec-based
       rebooting,  they	 then call kexec -e just before actually rebooting the
       machine. That way, the machine does  a  clean  shutdown	including  all
       shutdown scripts.

EXAMPLE
       For   example,	if   the  kernel  image	 you  want  to	reboot	to  is
       /boot/vmlinux, the contents of /proc/cmdline is root=/dev/hda1, and the
       path  to	 the  initrd is /boot/initrd, then you would use the following
       command to load the kernel:

	      kexec	 -l /boot/vmlinux	--append=root=/dev/hda1 --ini‐
	      trd=/boot/initrd

       After  this kernel is loaded, it can be booted to at any time using the
       command:

	      kexec -e


OPTIONS
       -e (--exec)
	      Run the currently loaded kernel. Note that it will  reboot  into
	      the loaded kernel without calling shutdown(8).

       -f (--force)
	      Force an immediate kexec call, do not call shutdown(8) (contrary
	      to the default action without any option parameter). This option
	      performs the same actions like executing -l and -e in one call.

       -h (--help)
	      Open a help file for kexec.

       -l (--load) kernel
	      Load the specified kernel into the current kernel.

       -p (--load-panic)
	      Load the new kernel for use on panic.

       -t (--type=type)
	      Specify that the new kernel is of this type.

       -u (--unload)
	      Unload  the  current kexec target kernel. If a capture kernel is
	      being unloaded then specify -p with -u.

       -v (--version)
	      Return the version number of the installed utility.

       -x (--no-ifdown)
	      Shut down the running  kernel,  but  restore  the	 interface  on
	      reload. (If this option is used, it must be specified last.)

       --mem-min=addr
	      Specify the lowest memory address addr to load code into.

       --mem-max=addr
	      Specify the highest memory address addr to load code into.

SUPPORTED KERNEL FILE TYPES AND OPTIONS
       Beoboot-x86

	      --args-elf
		     Pass ELF boot notes.

	      --args-linux
		     Pass Linux kernel style options.

	      -d  (--debug)
		     Enable debugging messages.

	      --real-mode
		     Use the kernel's real mode entry point.

       elf-x86

	      --append=string
		     Append string to the kernel command line.

	      --command-line=string
		     Set the kernel command line to string.

	      --reuse-cmdline
		     Use  the  command	line  from  the running system. When a
		     panic kernel is loaded, it strips the crashkernel parame‐
		     ter  automatically.  The  BOOT_IMAGE  parameter  is  also
		     stripped.

	      --initrd=file
		     Use file as the kernel's initial ramdisk.

	      --ramdisk=file
		     Use file as the kernel's initial ramdisk.

       bzImage-x86

	      --append=string
		     Append string to the kernel command line.

	      --command-line=string
		     Set the kernel command line to string.

	      --reuse-cmdline
		     Use the command line from	the  running  system.  When  a
		     panic kernel is loaded, it strips the crashkernel parame‐
		     ter  automatically.  The  BOOT_IMAGE  parameter  is  also
		     stripped.

	      --initrd=file
		     Use file as the kernel's initial ramdisk.

	      --ramdisk=file
		     Use file as the kernel's initial ramdisk.

	      --real-mode
		     Use real-mode entry point.

       multiboot-x86

	      --command-line=string
		     Set the kernel command line to string.

	      --reuse-cmdline
		     Use  the  command	line  from  the running system. When a
		     panic kernel is loaded, it strips the crashkernel parame‐
		     ter  automatically.  The  BOOT_IMAGE  parameter  is  also
		     stripped.

	      --module=mod arg1 arg2 ...
		     Load module mod with command-line arguments arg1 arg2 ...
		     This parameter can be specified multiple times.

ARCHITECTURE OPTIONS
       --console-serial
	      Enable the serial console.

       --console-vga
	      Enable the VGA console.

       --elf32-core-headers
	      Prepare core headers in ELF32 format.

       --elf64-core-headers
	      Prepare core headers in ELF64 format.

       --reset-vga
	      Attempt to reset a standard VGA device.

       --serial=port
	      Specify the serial port for debug output.

       --serial-baud=baud_rate
	      Specify the baud rate of the serial port.

Linux				  April 2006			      kexec(8)
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