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Diffstat (limited to 'kexec/kexec.8')
| -rw-r--r-- | kexec/kexec.8 | 399 |
1 files changed, 399 insertions, 0 deletions
diff --git a/kexec/kexec.8 b/kexec/kexec.8 new file mode 100644 index 0000000..3a344c5 --- /dev/null +++ b/kexec/kexec.8 @@ -0,0 +1,399 @@ +.\" Process this file with +.\" groff -man -Tascii kexec.8 +.\" +.TH kexec 8 "April 2006" Linux "User Manuals" +.SH NAME +kexec \- directly boot into a new kernel +.SH SYNOPSIS +.B /sbin/kexec +.B [-v (\-\-version)] [-f (\-\-force)] [-x (\-\-no-ifdown)] [-y (\-\-no-sync)] [-l (\-\-load)] [-p (\-\-load-panic)] [-u (\-\-unload)] [-e (\-\-exec)] [-t (\-\-type)] +.BI [\-\-mem\-min= addr ] +.BI [\-\-mem\-max= addr ] + +.SH DESCRIPTION +.B kexec +is a system call that enables you to load and boot into another +kernel from the currently running kernel. +.B kexec +performs the function of the boot loader from within the kernel. The +primary difference between a standard system boot and a +.B kexec +boot is that the hardware initialization normally performed by the BIOS +or firmware (depending on architecture) is not performed during a +.B kexec +boot. This has the effect of reducing the time required for a reboot. +.PP +Make sure you have selected +.B CONFIG_KEXEC=y +when configuring the kernel. The +.B CONFIG_KEXEC +option enables the +.B kexec +system call. +.SH USAGE +Using +.B kexec +consists of + +.RS +(1) loading the kernel to be rebooted to into memory, and +.RE +.RS +(2) actually rebooting to the pre-loaded kernel. +.RE +.PP +To load a kernel, the syntax is as follows: + +.RS +.B kexec +.RI \-l\ kernel-image +.RI "\-\-append=" command\-line\-options +.RI "\-\-initrd=" initrd\-image +.RE + +where +.I kernel\-image +is the kernel file that you intend to reboot to. +.PP +Insert the command-line parameters that must be passed to the new +kernel into +.IR command\-line\-options . +Passing the exact contents of /proc/cmdline into +.I command\-line\-options +is the safest way to ensure that correct values are passed to the +rebooting kernel. +.PP +The optional +.I initrd-image +is the initrd image to be used during boot. +.PP +It's also possible to invoke +.B kexec +without an option parameter. In that case, kexec loads the specified +kernel and then invokes +.BR shutdown (8). +If the shutdown scripts of your Linux distribution support +kexec-based rebooting, they then call +.B kexec +.I -e +just before actually rebooting the machine. That way, the machine does +a clean shutdown including all shutdown scripts. + +.SH EXAMPLE +.PP +For example, if the kernel image you want to reboot to is +.BR /boot/vmlinux , +the contents of /proc/cmdline is +.BR "root\=/dev/hda1" , +and the path to the initrd is +.BR /boot/initrd , +then you would use the following command to load the kernel: + +.RS +.B kexec +.RB \-l\ /boot/vmlinux +.RB "\-\-append=" "root=/dev/hda1" "\ \-\-initrd=" /boot/initrd +.RE +.PP +After this kernel is loaded, it can be booted to at any time using the +command: + +.RS +.BR kexec \ \-e +.RE + +.SH OPTIONS +.TP +.B \-d\ (\-\-debug) +Enable debugging messages. +.TP +.B \-S\ (\-\-status) +Return 1 if the type (by default crash) is loaded, 0 if not. Can be used in +conjuction with -l or -p to toggle the type. Note this option supersedes other +options and it will +.BR not\ load\ or\ unload\ the\ kernel. +.TP +.B \-e\ (\-\-exec) +Run the currently loaded kernel. Note that it will reboot into the loaded kernel without calling shutdown(8). +.TP +.B \-f\ (\-\-force) +Force an immediate +.B kexec +call, do not call +.BR shutdown (8) +(contrary to the default action without any option parameter). This option +performs the same actions like executing +.IR -l +and +.IR -e +in one call. +.TP +.B \-h\ (\-\-help) +Open a help file for +.BR kexec . +.TP +.B \-i\ (\-\-no-checks) +Fast reboot, no memory integrity checks. +.TP +.BI \-l\ (\-\-load) \ kernel +Load the specified +.I kernel +into the current kernel. +.TP +.B \-p\ (\-\-load\-panic) +Load the new kernel for use on panic. +.TP +.BI \-t\ (\-\-type= type ) +Specify that the new kernel is of this +.I type. +.TP +.BI \-s\ (\-\-kexec-file-syscall) +Specify that the new KEXEC_FILE_LOAD syscall should be used exclusively. +.TP +.BI \-c\ (\-\-kexec-syscall) +Specify that the old KEXEC_LOAD syscall should be used exclusively. +.TP +.BI \-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, so this is the default. + +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. +.TP +.B \-u\ (\-\-unload) +Unload the current +.B kexec +target kernel. If a capture kernel is being unloaded then specify -p with -u. +.TP +.B \-v\ (\-\-version) +Return the version number of the installed utility. +.TP +.B \-x\ (\-\-no\-ifdown) +Shut down the running kernel, but restore the interface on reload. +.TP +.B \-y\ (\-\-no\-sync) +Shut down the running kernel, but skip syncing the filesystems. +.TP +.BI \-\-mem\-min= addr +Specify the lowest memory address +.I addr +to load code into. +.TP +.BI \-\-mem\-max= addr +Specify the highest memory address +.I addr +to load code into. +.TP +.BI \-\-entry= addr +Specify the jump back address. (0 means it's not jump back or preserve context) +.TP +.BI \-\-load\-preserve\-context +Load the new kernel and preserve context of current kernel during kexec. +.TP +.BI \-\-load\-jump\-back\-helper +Load a helper image to jump back to original kernel. +.TP +.BI \-\-reuseinitrd +Reuse initrd from first boot. +.TP +.BI \-\-print-ckr-size +Print crash kernel region size, if available. + + +.SH SUPPORTED KERNEL FILE TYPES AND OPTIONS +.B Beoboot-x86 +.RS +.TP +.B \-\-args\-elf +Pass ELF boot notes. +.TP +.B \-\-args\-linux +Pass Linux kernel style options. +.TP +.B \-\-real\-mode +Use the kernel's real mode entry point. +.RE +.PP +.B elf-x86 +.RS +.TP +.BI \-\-append= string +Append +.I string +to the kernel command line. +.TP +.BI \-\-command\-line= string +Set the kernel command line to +.IR string . +.TP +.BI \-\-reuse-cmdline +Use the command line from the running system. When a panic kernel is loaded, it +strips the +.I +crashkernel +parameter automatically. The +.I BOOT_IMAGE +parameter is also stripped. +.TP +.BI \-\-initrd= file +Use +.I file +as the kernel's initial ramdisk. +.TP +.BI \-\-ramdisk= file +Use +.I file +as the kernel's initial ramdisk. +.RE +.PP +.B bzImage-x86 +.RS +.TP +.BI \-\-append= string +Append +.I string +to the kernel command line. +.TP +.BI \-\-command\-line= string +Set the kernel command line to +.IR string . +.TP +.BI \-\-reuse-cmdline +Use the command line from the running system. When a panic kernel is loaded, it +strips the +.I +crashkernel +parameter automatically. The +.I BOOT_IMAGE +parameter is also stripped. +.TP +.BI \-\-initrd= file +Use +.I file +as the kernel's initial ramdisk. +.TP +.BI \-\-ramdisk= file +Use +.I file +as the kernel's initial ramdisk. +.TP +.BI \-\-real-mode +Use real-mode entry point. +.RE +.PP +.B multiboot-x86 +.RS +.TP +.BI \-\-command\-line= string +Set the kernel command line to +.IR string . +.TP +.BI \-\-reuse-cmdline +Use the command line from the running system. When a panic kernel is loaded, it +strips the +.I +crashkernel +parameter automatically. The +.I BOOT_IMAGE +parameter is also stripped. +.TP +.BI \-\-module= "mod arg1 arg2 ..." +Load module +.I mod +with command-line arguments +.I "arg1 arg2 ..." +This parameter can be specified multiple times. +.RE +.PP +.B multiboot2-x86 +.RS +.TP +.BI \-\-command\-line= string +Set the kernel command line to +.IR string . +.TP +.BI \-\-reuse-cmdline +Use the command line from the running system. When a panic kernel is loaded, it +strips the +.I +crashkernel +parameter automatically. The +.I BOOT_IMAGE +parameter is also stripped. +.TP +.BI \-\-module= "mod arg1 arg2 ..." +Load module +.I mod +with command-line arguments +.I "arg1 arg2 ..." +This parameter can be specified multiple times. +.RE +.PP +.B elf-ppc64 +.RS +.TP +.BI \-\-reuse-cmdline +Use the kernel command line from the running system. +.TP +.BI \-\-command\-line= string +Set the kernel command line to +.IR string. +.TP +.BI \-\-append= string +Set the kernel command line to +.IR string. +.TP +.BI \-\-ramdisk= file +Use +.IR file +as the initial RAM disk. +.TP +.BI \-\-initrd= file +Use +.IR file +as the initial RAM disk. +.TP +.BI \-\-devicetreeblob= file +Specify device tree blob file. Not applicable while using --kexec-file-syscall. +.TP +.BI \-\-dtb= file +Specify device tree blob file. Not applicable while using --kexec-file-syscall. +.RE + +.SH ARCHITECTURE OPTIONS +.TP +.B \-\-console\-serial +Enable the serial console. +.TP +.B \-\-console\-vga +Enable the VGA console. +.TP +.B \-\-elf32\-core\-headers +Prepare core headers in ELF32 format. +.TP +.B \-\-elf64\-core\-headers +Prepare core headers in ELF64 format. +.TP +.B \-\-reset\-vga +Attempt to reset a standard VGA device. +.TP +.BI \-\-serial= port +Specify the serial +.I port +for debug output. +.TP +.BI \-\-serial\-baud= baud_rate +Specify the +.I baud rate +of the serial port. +.TP +.BI \-\-dt\-no\-old\-root +Do not reuse old kernel root=<device> +param while creating flatten device tree. |