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)]
I [--mem-min= addr ]
I [--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
--initrd=initrd-image
where
kernel-image
is the kernel file that you intend to reboot to.
Note: Compressed kernel images such as bzImage are not supported by
R kexec .
Use the uncompressed vmlinux.
Insert the command-line parameters that must be passed to the new
kernel into
R 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.
EXAMPLE
For example, if the kernel image you want to reboot to is
R /boot/vmlinux ,
the contents of /proc/cmdline is
R root\=/dev/hda1 ,
and the path to the initrd is
R /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:
R kexec -e
OPTIONS
-e (--exec)
Run the currently loaded kernel.
-f (--force)
Force an immediate
kexec
call, do not call shutdown.
-h (--help)
Open a help file for
R kexec .
I -l (--load) kernel
Load the specified
kernel
into the current kernel.
-p (--load-panic)
Load the new kernel for use on panic.
I -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.)
I --mem-min= addr
Specify the lowest memory address
addr
to load code into.
I --mem-max= addr
Specify the highest memory address
addr
to load code into.
SUPPORTED KERNEL FILE TYPES AND OPTIONS
--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.
I --append= string
Append
string
to the kernel command line.
I --command-line= string
Set the kernel command line to
R string .
I --initrd= file
Use
file
as the kernel's initial ramdisk.
I --ramdisk= file
Use
file
as the kernel's initial ramdisk.
I --command-line= string
Set the kernel command line to
R string .
I --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.
I --serial= port
Specify the serial
port
for debug output.
I --serial-baud= baud_rate
Specify the
baud rate
of the serial port.
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