[PATCH 0/2] kexec jump/hibernation support for kexec-tools
ying.huang at intel.com
Tue Oct 28 23:24:13 EDT 2008
This patchset add kexec jump/hibernation support to kexec
tools. Together with the kexec jump/hibernation features in Linux
kernel (which is merged into mainstream from 2.6.27 on) can be used
- A simple hibernation implementation without ACPI support. You can
kexec a hibernating kernel, save the memory image of original system
and shutdown the system. When resuming, you restore the memory image
of original system via ordinary kexec load then jump back.
- Kernel/system debug through making system snapshot. You can make
system snapshot with kexec/kdump, jump back, do some thing and make
another system snapshot.
- Cooperative multi-kernel/system. With kexec jump, you can switch
between several kernels/systems quickly without boot process except
the first time. This appears like swap a whole kernel/system out/in.
- A general method to call program in physical mode (paging turning
off). This can be used to invoke BIOS code under Linux.
The following additional kernel/tools may be needed for kexec
- Linux kernel from 2.6.27 on.
- makedumpfile with patches are used as memory image saving tool, it
can exclude free pages from original kernel memory image file. The
patches and the precompiled makedumpfile can be download from the
- An initramfs image can be used as the root file system of kexeced
kernel. An initramfs image built with "BuildRoot" can be downloaded
from the following URL:
initramfs image: http://khibernation.sourceforge.net/download/release_v10/initramfs/rootfs_cvs_kh10.gz
All user space tools above are included in the initramfs image.
Usage example of simple hibernation:
1. Compile and install Linux kernel (newer than 2.6.27) with following
2. Build an initramfs image contains kexec-tool and makedumpfile, or
download the pre-built initramfs image, called rootfs.gz in
3. Prepare a partition to save memory image of original kernel, called
hibernating partition in following text.
4. Boot kernel compiled in step 1 (kernel A).
5. In the kernel A, load kernel compiled in step 1 (kernel B) with
/sbin/kexec. The shell command line can be as follow:
/sbin/kexec --load-preserve-context /boot/bzImage --mem-max=0xffffff --initrd=rootfs.gz
6. Boot the kernel B with following shell command line:
7. The kernel B will boot as normal kexec. In kernel B the memory
image of kernel A can be saved into hibernating partition as
jump_back_entry=`cat /proc/cmdline | tr ' ' '\n' | grep kexec_jump_back_entry | cut -d '='`
echo $jump_back_entry > kexec_jump_back_entry
cp /proc/vmcore dump.elf
Then you can shutdown the machine as normal.
8. Boot kernel compiled in step 1 (kernel C). Use the rootfs.gz as
root file system.
9. In kernel C, load the memory image of kernel A as follow:
/sbin/kexec -l --args-none --entry=`cat kexec_jump_back_entry` dump.elf
10. Jump back to the kernel A as follow:
Then, kernel A is resumed.
Now, only the i386 architecture is supported. The patchset is based on
the latest kexec-tools git tree, and has been tested on IBM T42 with
ACPI on and off.
Signed-off-by: Huang Ying <ying.huang at intel.com>
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