Man Pages

kexec(8) - phpMan kexec(8) - phpMan

Command: man perldoc info search(apropos)  


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 stan-
       dard 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 shutdown(1).  If the shutdown scripts of your Linux distribution support  kexec-based  reboot-
       ing,  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 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 parameter 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 parameter 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 multi-
                     ple 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)