memory image to a dump file on the local disk, or across the network to
a remote system.
-Kdump and kexec are currently supported on the x86, x86_64, ppc64 and IA64
+Kdump and kexec are currently supported on the x86, x86_64, ppc64 and ia64
architectures.
When the system kernel boots, it reserves a small section of memory for
regardless of where the kernel loads. Therefore, kexec backs up this
region just before rebooting into the dump-capture kernel.
+Similarly on PPC64 machines first 32KB of physical memory is needed for
+booting regardless of where the kernel is loaded and to support 64K page
+size kexec backs up the first 64KB memory.
+
All of the necessary information about the system kernel's core image is
encoded in the ELF format, and stored in a reserved area of memory
before a crash. The physical address of the start of the ELF header is
2) Download the kexec-tools user-space package from the following URL:
-http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-tools-testing-20061214.tar.gz
+http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-tools-testing.tar.gz
+
+This is a symlink to the latest version, which at the time of writing is
+20061214, the only release of kexec-tools-testing so far. As other versions
+are made released, the older onese will remain available at
+http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/
Note: Latest kexec-tools-testing git tree is available at
3) Unpack the tarball with the tar command, as follows:
- tar xvpzf kexec-tools-testing-20061214.tar.gz
+ tar xvpzf kexec-tools-testing.tar.gz
-4) Change to the kexec-tools-1.101 directory, as follows:
+4) Change to the kexec-tools directory, as follows:
- cd kexec-tools-testing-20061214
+ cd kexec-tools-testing-VERSION
5) Configure the package, as follows:
Dump-capture kernel config options (Arch Dependent, ppc64)
----------------------------------------------------------
-- Make and install the kernel and its modules. DO NOT add this kernel
+* Make and install the kernel and its modules. DO NOT add this kernel
to the boot loader configuration files.
Dump-capture kernel config options (Arch Dependent, ia64)
----------------------------------------------------------
-(To be filled)
+
+- No specific options are required to create a dump-capture kernel
+ for ia64, other than those specified in the arch idependent section
+ above. This means that it is possible to use the system kernel
+ as a dump-capture kernel if desired.
+
+ The crashkernel region can be automatically placed by the system
+ kernel at run time. This is done by specifying the base address as 0,
+ or omitting it all together.
+
+ crashkernel=256M@0
+ or
+ crashkernel=256M
+
+ If the start address is specified, note that the start address of the
+ kernel will be aligned to 64Mb, so if the start address is not then
+ any space below the alignment point will be wasted.
Boot into System Kernel
=======================
-1) Make and install the kernel and its modules. Update the boot loader
- (such as grub, yaboot, or lilo) configuration files as necessary.
+1) Update the boot loader (such as grub, yaboot, or lilo) configuration
+ files as necessary.
2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
where Y specifies how much memory to reserve for the dump-capture kernel
On ppc64, use "crashkernel=128M@32M".
+ On ia64, 256M@256M is a generous value that typically works.
+ The region may be automatically placed on ia64, see the
+ dump-capture kernel config option notes above.
+
Load the Dump-capture Kernel
============================
For ppc64:
- Use vmlinux
For ia64:
- (To be filled)
+ - Use vmlinux or vmlinuz.gz
+
If you are using a uncompressed vmlinux image then use following command
to load dump-capture kernel.
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"
+Please note, that --args-linux does not need to be specified for ia64.
+It is planned to make this a no-op on that architecture, but for now
+it should be omitted
+
Following are the arch specific command line options to be used while
loading dump-capture kernel.
-For i386 and x86_64:
- "init 1 irqpoll maxcpus=1"
+For i386, x86_64 and ia64:
+ "1 irqpoll maxcpus=1"
For ppc64:
- "init 1 maxcpus=1 noirqdistrib"
-
-For IA64
- (To be filled)
+ "1 maxcpus=1 noirqdistrib"
Notes on loading the dump-capture kernel:
* You must specify <root-dev> in the format corresponding to the root
device name in the output of mount command.
-* "init 1" boots the dump-capture kernel into single-user mode without
- networking. If you want networking, use "init 3."
+* Boot parameter "1" boots the dump-capture kernel into single-user
+ mode without networking. If you want networking, use "3".
* We generally don' have to bring up a SMP kernel just to capture the
dump. Hence generally it is useful either to build a UP dump-capture
is called inside interrupt context or die() is called and panic_on_oops is set,
the system will boot into the dump-capture kernel.
-On powererpc systems when a soft-reset is generated, die() is called by all cpus and the system will boot into the dump-capture kernel.
+On powererpc systems when a soft-reset is generated, die() is called by all cpus
+and the system will boot into the dump-capture kernel.
For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
-"echo c > /proc/sysrq-trigger or write a module to force the panic.
+"echo c > /proc/sysrq-trigger" or write a module to force the panic.
Write Out the Dump File
=======================
To Do
=====
-1) Provide a kernel pages filtering mechanism, so core file size is not
- extreme on systems with huge memory banks.
-
-2) Relocatable kernel can help in maintaining multiple kernels for
- crash_dump, and the same kernel as the system kernel can be used to
- capture the dump.
+1) Provide relocatable kernels for all architectures to help in maintaining
+ multiple kernels for crash_dump, and the same kernel as the system kernel
+ can be used to capture the dump.
Contact
git.openpandora.org / pandora-kernel.git / blobdiff