kexec(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | USAGE | EXAMPLE | OPTIONS | SUPPORTED KERNEL FILE TYPES AND OPTIONS | ARCHITECTURE OPTIONS | COLOPHON

kexec(8)                      User Manuals                      kexec(8)

NAME         top

       kexec - directly boot into a new kernel

SYNOPSIS         top

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

DESCRIPTION         top

       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         top

       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(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         top

       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         top

       -d (--debug)
              Enable debugging messages.

       -S (--status)
              Return 0 if the type (by default crash) is loaded. Can be
              used in conjuction with -l or -p to toggle the type. Note
              this option supersedes other options and it will
              not load or unload the kernel.

       -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.

       -i (--no-checks)
              Fast reboot, no memory integrity checks.

       -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.

       -s (--kexec-file-syscall)
              Specify that the new KEXEC_FILE_LOAD syscall should be
              used exclusively.

       -c (--kexec-syscall)
              Specify that the old KEXEC_LOAD syscall should be used
              exclusively (the default).

       -a (--kexec-syscall-auto)
              Try the new KEXEC_FILE_LOAD syscall first and when it is
              not supported or the kernel does not understand the
              supplied image fall back to the old KEXEC_LOAD interface.

              There is no one single interface that always works.

              KEXEC_FILE_LOAD is required on systems that use locked-
              down secure boot to verify the kernel signature.
              KEXEC_LOAD may be also disabled in the kernel
              configuration.

              KEXEC_LOAD is required for some kernel image formats and
              on architectures that do not implement KEXEC_FILE_LOAD.

       -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.

       -y (--no-sync)
              Shut down the running kernel, but skip syncing the
              filesystems.

       --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.

       --entry=addr
              Specify the jump back address. (0 means it's not jump back
              or preserve context)

       --load-preserve-context
              Load the new kernel and preserve context of current kernel
              during kexec.

       --load-jump-back-helper
              Load a helper image to jump back to original kernel.

       --reuseinitrd
              Reuse initrd from first boot.

       --print-ckr-size
              Print crash kernel region size, if available.

SUPPORTED KERNEL FILE TYPES AND OPTIONS         top

       Beoboot-x86

              --args-elf
                     Pass ELF boot notes.

              --args-linux
                     Pass Linux kernel style options.

              --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 multiple
                     times.

       multiboot2-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 multiple
                     times.

ARCHITECTURE OPTIONS         top

       --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.

COLOPHON         top

       This page is part of the kexec-tools (kexec-tools) project.
       Information about the project can be found at [unknown -- if you
       know, please contact man-pages@man7.org] It is not known how to
       report bugs for this man page; if you know, please send a mail to
       man-pages@man7.org.  This page was obtained from the project's
       upstream Git repository
       ⟨https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git⟩
       on 2020-12-18.  (At that time, the date of the most recent commit
       that was found in the repository was 2020-12-17.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Linux                          April 2006                       kexec(8)

Pages that refer to this page: kexec_load(2)