the system panics). The system kernel's memory image is preserved across
the reboot and is accessible to the dump-capture kernel.
-You can use common Linux commands, such as cp and scp, to copy the
+You can use common commands, such as cp and scp, to copy the
memory image to a dump file on the local disk, or across the network to
a remote system.
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.tar.gz
+http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-tools.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/
+This is a symlink to the latest version.
-Note: Latest kexec-tools-testing git tree is available at
+The latest kexec-tools git tree is available at:
-git://git.kernel.org/pub/scm/linux/kernel/git/horms/kexec-tools-testing.git
+git://git.kernel.org/pub/scm/linux/kernel/git/horms/kexec-tools.git
or
-http://www.kernel.org/git/?p=linux/kernel/git/horms/kexec-tools-testing.git;a=summary
+http://www.kernel.org/git/?p=linux/kernel/git/horms/kexec-tools.git
+
+More information about kexec-tools can be found at
+http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/README.html
3) Unpack the tarball with the tar command, as follows:
- tar xvpzf kexec-tools-testing.tar.gz
+ tar xvpzf kexec-tools.tar.gz
4) Change to the kexec-tools directory, as follows:
- cd kexec-tools-testing-VERSION
+ cd kexec-tools-VERSION
5) Configure the package, as follows:
2) Or use the system kernel binary itself as dump-capture kernel and there is
no need to build a separate dump-capture kernel. This is possible
- only with the architecutres which support a relocatable kernel. As
- of today i386 and ia64 architectures support relocatable kernel.
+ only with the architectures which support a relocatable kernel. As
+ of today, i386, x86_64, ppc64 and ia64 architectures support relocatable
+ kernel.
Building a relocatable kernel is advantageous from the point of view that
one does not have to build a second kernel for capturing the dump. But
CONFIG_PROC_VMCORE=y
(CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
-Dump-capture kernel config options (Arch Dependent, i386)
---------------------------------------------------------
-1) On x86, enable high memory support under "Processor type and
+Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
+--------------------------------------------------------------------
+
+1) On i386, enable high memory support under "Processor type and
features":
CONFIG_HIGHMEM64G=y
or
CONFIG_HIGHMEM4G
-2) On x86 and x86_64, disable symmetric multi-processing support
+2) On i386 and x86_64, disable symmetric multi-processing support
under "Processor type and features":
CONFIG_SMP=n
5) 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, x86_64)
+Dump-capture kernel config options (Arch Dependent, ppc64)
----------------------------------------------------------
-1) On x86 and x86_64, disable symmetric multi-processing support
- under "Processor type and features":
- CONFIG_SMP=n
+1) Enable "Build a kdump crash kernel" support under "Kernel" options:
- (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
- when loading the dump-capture kernel, see section "Load the Dump-capture
- Kernel".)
-
-2) Use a suitable value for "Physical address where the kernel is
- loaded" (under "Processor type and features"). This only appears when
- "kernel crash dumps" is enabled. By default this value is 0x1000000
- (16MB). It should be the same as X in the "crashkernel=Y@X" boot
- parameter.
+ CONFIG_CRASH_DUMP=y
- For x86_64, normally "CONFIG_PHYSICAL_START=0x1000000".
+2) Enable "Build a relocatable kernel" support
-3) Make and install the kernel and its modules. DO NOT add this kernel
- to the boot loader configuration files.
+ CONFIG_RELOCATABLE=y
-Dump-capture kernel config options (Arch Dependent, ppc64)
-----------------------------------------------------------
-
-* Make and install the kernel and its modules. DO NOT add this kernel
- to the boot loader configuration files.
+ Make and install the kernel and its modules.
Dump-capture kernel config options (Arch Dependent, ia64)
----------------------------------------------------------
- No specific options are required to create a dump-capture kernel
- for ia64, other than those specified in the arch idependent section
+ for ia64, other than those specified in the arch independent section
above. This means that it is possible to use the system kernel
as a dump-capture kernel if desired.
any space below the alignment point will be wasted.
+Extended crashkernel syntax
+===========================
+
+While the "crashkernel=size[@offset]" syntax is sufficient for most
+configurations, sometimes it's handy to have the reserved memory dependent
+on the value of System RAM -- that's mostly for distributors that pre-setup
+the kernel command line to avoid a unbootable system after some memory has
+been removed from the machine.
+
+The syntax is:
+
+ crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
+ range=start-[end]
+
+ 'start' is inclusive and 'end' is exclusive.
+
+For example:
+
+ crashkernel=512M-2G:64M,2G-:128M
+
+This would mean:
+
+ 1) if the RAM is smaller than 512M, then don't reserve anything
+ (this is the "rescue" case)
+ 2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
+ 3) if the RAM size is larger than 2G, then reserve 128M
+
+
+
Boot into System Kernel
=======================
can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
of dump-capture kernel. Following is the summary.
-For i386:
+For i386 and x86_64:
- Use vmlinux if kernel is not relocatable.
- Use bzImage/vmlinuz if kernel is relocatable.
-For x86_64:
- - Use vmlinux
For ppc64:
- Use vmlinux
For ia64:
loading dump-capture kernel.
For i386, x86_64 and ia64:
- "1 irqpoll maxcpus=1"
+ "1 irqpoll maxcpus=1 reset_devices"
For ppc64:
- "1 maxcpus=1 noirqdistrib"
+ "1 maxcpus=1 noirqdistrib reset_devices"
Notes on loading the dump-capture kernel:
* By default, the ELF headers are stored in ELF64 format to support
- systems with more than 4GB memory. The --elf32-core-headers option can
- be used to force the generation of ELF32 headers. This is necessary
- because GDB currently cannot open vmcore files with ELF64 headers on
- 32-bit systems. ELF32 headers can be used on non-PAE systems (that is,
- less than 4GB of memory).
+ systems with more than 4GB memory. On i386, kexec automatically checks if
+ the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
+ So, on non-PAE systems, ELF32 is always used.
+
+ The --elf32-core-headers option can be used to force the generation of ELF32
+ headers. This is necessary because GDB currently cannot open vmcore files
+ with ELF64 headers on 32-bit systems.
* The "irqpoll" boot parameter reduces driver initialization failures
due to shared interrupts in the dump-capture kernel.
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
+On powerpc 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",
Vivek Goyal (vgoyal@in.ibm.com)
Maneesh Soni (maneesh@in.ibm.com)
-
-Trademark
-=========
-
-Linux is a trademark of Linus Torvalds in the United States, other
-countries, or both.