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NAME | SYNOPSIS | DESCRIPTION | USAGE | EXAMPLE | OPTIONS | SUPPORTED KERNEL FILE TYPES AND OPTIONS | ARCHITECTURE OPTIONS | COLOPHON |
kexec(8) User Manuals kexec(8)
kexec - directly boot into a new kernel
/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]
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.
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.
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
-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.
-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.
-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.
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.
--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.
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
2017-07-05. If you discover any rendering problems in this HTML ver‐
sion 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 man‐
ual page), send a mail to man-pages@man7.org
Linux April 2006 kexec(8)
Pages that refer to this page: kexec_load(2)