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  func-
       tion 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 --initrd=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 kernel 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  shut-
       down(1).   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 --initrd=/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.

       -f (--force)
	      Force  an  immediate  kexec call, do not call shutdown(1) (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  parameter  automati-
		     cally. 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 parameter automati-
		     cally. 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  parameter  automati-
		     cally. 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)