run a null modem to a second machine and capture the output there
using your favourite communication program. Minicom works well.
-(3) Use Kdump (see Documentation/kdump/kdump.txt),
+(3) Use Kdump (see Documentation/kdump/kdump.rst),
extract the kernel ring buffer from old memory with using dmesg
gdbmacro in Documentation/kdump/gdbmacros.txt.
[KNL, x86_64] select a region under 4G first, and
fall back to reserve region above 4G when '@offset'
hasn't been specified.
- See Documentation/kdump/kdump.txt for further details.
+ See Documentation/kdump/kdump.rst for further details.
crashkernel=range1:size1[,range2:size2,...][@offset]
[KNL] Same as above, but depends on the memory
in the running system. The syntax of range is
start-[end] where start and end are both
a memory unit (amount[KMG]). See also
- Documentation/kdump/kdump.txt for an example.
+ Documentation/kdump/kdump.rst for an example.
crashkernel=size[KMG],high
[KNL, x86_64] range could be above 4G. Allow kernel
Specifies physical address of start of kernel core
image elf header and optionally the size. Generally
kexec loader will pass this option to capture kernel.
- See Documentation/kdump/kdump.txt for details.
+ See Documentation/kdump/kdump.rst for details.
enable_mtrr_cleanup [X86]
The kernel tries to adjust MTRR layout from continuous
--- /dev/null
+:orphan:
+
+================================================================
+Documentation for Kdump - The kexec-based Crash Dumping Solution
+================================================================
+
+This document includes overview, setup and installation, and analysis
+information.
+
+.. toctree::
+ :maxdepth: 1
+
+ kdump
+ vmcoreinfo
+
+.. only:: subproject and html
+
+ Indices
+ =======
+
+ * :ref:`genindex`
The latest kexec-tools git tree is available at:
-git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
-and
-http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
+- git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
+- http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
There is also a gitweb interface available at
http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git
More information about kexec-tools can be found at
http://horms.net/projects/kexec/
-3) Unpack the tarball with the tar command, as follows:
+3) Unpack the tarball with the tar command, as follows::
- tar xvpzf kexec-tools.tar.gz
+ tar xvpzf kexec-tools.tar.gz
-4) Change to the kexec-tools directory, as follows:
+4) Change to the kexec-tools directory, as follows::
- cd kexec-tools-VERSION
+ cd kexec-tools-VERSION
-5) Configure the package, as follows:
+5) Configure the package, as follows::
- ./configure
+ ./configure
-6) Compile the package, as follows:
+6) Compile the package, as follows::
- make
+ make
-7) Install the package, as follows:
+7) Install the package, as follows::
- make install
+ make install
Build the system and dump-capture kernels
System kernel config options
----------------------------
-1) Enable "kexec system call" in "Processor type and features."
+1) Enable "kexec system call" in "Processor type and features."::
- CONFIG_KEXEC=y
+ CONFIG_KEXEC=y
2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
- filesystems." This is usually enabled by default.
+ filesystems." This is usually enabled by default::
- CONFIG_SYSFS=y
+ CONFIG_SYSFS=y
Note that "sysfs file system support" might not appear in the "Pseudo
filesystems" menu if "Configure standard kernel features (for small
systems)" is not enabled in "General Setup." In this case, check the
- .config file itself to ensure that sysfs is turned on, as follows:
+ .config file itself to ensure that sysfs is turned on, as follows::
- grep 'CONFIG_SYSFS' .config
+ grep 'CONFIG_SYSFS' .config
-3) Enable "Compile the kernel with debug info" in "Kernel hacking."
+3) Enable "Compile the kernel with debug info" in "Kernel hacking."::
- CONFIG_DEBUG_INFO=Y
+ CONFIG_DEBUG_INFO=Y
This causes the kernel to be built with debug symbols. The dump
analysis tools require a vmlinux with debug symbols in order to read
-----------------------------------------------------
1) Enable "kernel crash dumps" support under "Processor type and
- features":
+ features"::
- CONFIG_CRASH_DUMP=y
+ CONFIG_CRASH_DUMP=y
-2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems".
+2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems"::
+
+ CONFIG_PROC_VMCORE=y
- 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 and x86_64)
--------------------------------------------------------------------
1) On i386, enable high memory support under "Processor type and
- features":
+ features"::
+
+ CONFIG_HIGHMEM64G=y
+
+ or::
- CONFIG_HIGHMEM64G=y
- or
- CONFIG_HIGHMEM4G
+ CONFIG_HIGHMEM4G
2) On i386 and x86_64, disable symmetric multi-processing support
- under "Processor type and features":
+ under "Processor type and features"::
- CONFIG_SMP=n
+ CONFIG_SMP=n
(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
3) If one wants to build and use a relocatable kernel,
Enable "Build a relocatable kernel" support under "Processor type and
- features"
+ features"::
- CONFIG_RELOCATABLE=y
+ CONFIG_RELOCATABLE=y
4) Use a suitable value for "Physical address where the kernel is
loaded" (under "Processor type and features"). This only appears when
Dump-capture kernel config options (Arch Dependent, ppc64)
----------------------------------------------------------
-1) Enable "Build a kdump crash kernel" support under "Kernel" options:
+1) Enable "Build a kdump crash kernel" support under "Kernel" options::
- CONFIG_CRASH_DUMP=y
+ CONFIG_CRASH_DUMP=y
-2) Enable "Build a relocatable kernel" support
+2) Enable "Build a relocatable kernel" support::
- CONFIG_RELOCATABLE=y
+ CONFIG_RELOCATABLE=y
Make and install the kernel and its modules.
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.
+ or omitting it all together::
- crashkernel=256M@0
- or
- crashkernel=256M
+ 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
----------------------------------------------------------
- To use a relocatable kernel,
- Enable "AUTO_ZRELADDR" support under "Boot" options:
+ Enable "AUTO_ZRELADDR" support under "Boot" options::
- AUTO_ZRELADDR=y
+ AUTO_ZRELADDR=y
Dump-capture kernel config options (Arch Dependent, arm64)
----------------------------------------------------------
the kernel command line to avoid a unbootable system after some memory has
been removed from the machine.
-The syntax is:
+The syntax is::
crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
range=start-[end]
-For example:
+For example::
crashkernel=512M-2G:64M,2G-:128M
of dump-capture kernel. Following is the summary.
For i386 and x86_64:
+
- Use vmlinux if kernel is not relocatable.
- Use bzImage/vmlinuz if kernel is relocatable.
+
For ppc64:
+
- Use vmlinux
+
For ia64:
+
- Use vmlinux or vmlinuz.gz
+
For s390x:
+
- Use image or bzImage
+
For arm:
+
- Use zImage
+
For arm64:
+
- Use vmlinux or Image
If you are using an uncompressed vmlinux image then use following command
-to load dump-capture kernel.
+to load dump-capture kernel::
kexec -p <dump-capture-kernel-vmlinux-image> \
--initrd=<initrd-for-dump-capture-kernel> --args-linux \
--append="root=<root-dev> <arch-specific-options>"
If you are using a compressed bzImage/vmlinuz, then use following command
-to load dump-capture kernel.
+to load dump-capture kernel::
kexec -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"
If you are using a compressed zImage, then use following command
-to load dump-capture kernel.
+to load dump-capture kernel::
kexec --type zImage -p <dump-capture-kernel-bzImage> \
--initrd=<initrd-for-dump-capture-kernel> \
--append="root=<root-dev> <arch-specific-options>"
If you are using an uncompressed Image, then use following command
-to load dump-capture kernel.
+to load dump-capture kernel::
kexec -p <dump-capture-kernel-Image> \
--initrd=<initrd-for-dump-capture-kernel> \
loading dump-capture kernel.
For i386, x86_64 and ia64:
+
"1 irqpoll maxcpus=1 reset_devices"
For ppc64:
+
"1 maxcpus=1 noirqdistrib reset_devices"
For s390x:
+
"1 maxcpus=1 cgroup_disable=memory"
For arm:
+
"1 maxcpus=1 reset_devices"
For arm64:
+
"1 maxcpus=1 reset_devices"
Notes on loading the dump-capture kernel:
=======================
After the dump-capture kernel is booted, write out the dump file with
-the following command:
+the following command::
cp /proc/vmcore <dump-file>
You can do limited analysis using GDB on the dump file copied out of
/proc/vmcore. Use the debug vmlinux built with -g and run the following
-command:
+command::
gdb vmlinux <dump-file>
Contact
=======
-Vivek Goyal (vgoyal@redhat.com)
-Maneesh Soni (maneesh@in.ibm.com)
+- Vivek Goyal (vgoyal@redhat.com)
+- Maneesh Soni (maneesh@in.ibm.com)
+
+GDB macros
+==========
+.. include:: gdbmacros.txt
+ :literal:
-================================================================
- VMCOREINFO
-================================================================
+==========
+VMCOREINFO
+==========
-===========
What is it?
===========
section and used by user-space tools like crash and makedumpfile to
analyze a kernel's memory layout.
-================
Common variables
================
which nodes are in the system and online.
swapper_pg_dir
--------------
+--------------
The global page directory pointer of the kernel. Used to translate
virtual to physical addresses.
The size of a nodemask_t type. Used to compute the number of online
nodes.
-(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|
- compound_order|compound_head)
--------------------------------------------------------------------
+(page, flags|_refcount|mapping|lru|_mapcount|private|compound_dtor|compound_order|compound_head)
+-------------------------------------------------------------------------------------------------
User-space tools compute their values based on the offset of these
variables. The variables are used when excluding unnecessary pages.
-(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_
- spanned_pages|node_id)
--------------------------------------------------------------------
+(pglist_data, node_zones|nr_zones|node_mem_map|node_start_pfn|node_spanned_pages|node_id)
+-----------------------------------------------------------------------------------------
On NUMA machines, each NUMA node has a pg_data_t to describe its memory
layout. On UMA machines there is a single pglist_data which describes the
On linux-2.6.21 or later, the number of free pages is in
vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
-PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision
-|PG_head_mask|PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)
-|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
------------------------------------------------------------------
+PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision|PG_head_mask
+------------------------------------------------------------------------------
Page attributes. These flags are used to filter various unnecessary for
dumping pages.
+PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy)|PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline)
+-----------------------------------------------------------------------------
+
+More page attributes. These flags are used to filter various unnecessary for
+dumping pages.
+
+
HUGETLB_PAGE_DTOR
-----------------
The HUGETLB_PAGE_DTOR flag denotes hugetlbfs pages. Makedumpfile
excludes these pages.
-======
x86_64
======
Currently, sme_mask stores the value of the C-bit position. If needed,
additional SME-relevant info can be placed in that variable.
-For example:
-[ misc ][ enc bit ][ other misc SME info ]
-0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
-63 59 55 51 47 43 39 35 31 27 ... 3
+For example::
+
+ [ misc ][ enc bit ][ other misc SME info ]
+ 0000_0000_0000_0000_1000_0000_0000_0000_0000_0000_..._0000
+ 63 59 55 51 47 43 39 35 31 27 ... 3
-======
x86_32
======
table space per process. Used to check whether PAE was enabled in the
crash kernel when converting virtual addresses to physical addresses.
-====
ia64
====
User-space tools need to know whether the crash kernel was in 3-level or
4-level paging mode. Used to distinguish the page table.
-=====
ARM64
=====
The kernel randomization offset. Used to compute the page offset. If
KASLR is disabled, this value is zero.
-====
arm
-====
+===
ARM_LPAE
--------
It indicates whether the crash kernel supports large physical address
extensions. Used to translate virtual to physical addresses.
-====
s390
====
lowcore_ptr
-----------
+-----------
An array with a pointer to the lowcore of every CPU. Used to print the
psw and all registers information.
The maximum number of CPUs.
-=======
powerpc
=======
Used to make vtop translations.
-vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|
-(vmemmap_backing, virt_addr)
-----------------------------------------------------------------
+vmemmap_backing|(vmemmap_backing, list)|(vmemmap_backing, phys)|(vmemmap_backing, virt_addr)
+--------------------------------------------------------------------------------------------
The vmemmap virtual address space management does not have a traditional
page table to track which virtual struct pages are backed by a physical
Used in vtop translations.
-==
sh
==
the default calculated size. Use this option if default
boot memory size is not sufficient for second kernel to
boot successfully. For syntax of crashkernel= parameter,
- refer to Documentation/kdump/kdump.txt. If any offset is
+ refer to Documentation/kdump/kdump.rst. If any offset is
provided in crashkernel= parameter, it will be ignored
as fadump uses a predefined offset to reserve memory
for boot memory dump preservation in case of a crash.
(2)用串口终端启动(请参看Documentation/admin-guide/serial-console.rst),运行一个null
modem到另一台机器并用你喜欢的通讯工具获取输出。Minicom工作地很好。
-(3)使用Kdump(请参看Documentation/kdump/kdump.txt),
+(3)使用Kdump(请参看Documentation/kdump/kdump.rst),
使用在Documentation/kdump/gdbmacros.txt中定义的dmesg gdb宏,从旧的内存中提取内核
环形缓冲区。
and loop forever. This is generally not what a watchdog user wants.
For those wishing to learn more please see:
- Documentation/kdump/kdump.txt
+ Documentation/kdump/kdump.rst
Documentation/admin-guide/kernel-parameters.txt (panic=)
Your Linux Distribution specific documentation.
kdump/kexec. The crash dump kernel must be compiled to a
memory address not used by the main kernel
- For more details see Documentation/kdump/kdump.txt
+ For more details see Documentation/kdump/kdump.rst
config AUTO_ZRELADDR
bool "Auto calculation of the decompressed kernel image address"
reserved region and then later executed after a crash by
kdump/kexec.
- For more details see Documentation/kdump/kdump.txt
+ For more details see Documentation/kdump/kdump.rst
config XEN_DOM0
def_bool y
to a memory address not used by the main kernel using
PHYSICAL_START.
- For more details see Documentation/kdump/kdump.txt
+ For more details see Documentation/kdump/kdump.rst
config KEXEC_JUMP
bool "kexec jump (EXPERIMENTAL)"
to a memory address not used by the main kernel or BIOS using
PHYSICAL_START, or it must be built as a relocatable image
(CONFIG_RELOCATABLE=y).
- For more details see Documentation/kdump/kdump.txt
+ For more details see Documentation/kdump/kdump.rst
config KEXEC_JUMP
bool "kexec jump"
the reserved region. In other words, it can be set based on
the "X" value as specified in the "crashkernel=YM@XM"
command line boot parameter passed to the panic-ed
- kernel. Please take a look at Documentation/kdump/kdump.txt
+ kernel. Please take a look at Documentation/kdump/kdump.rst
for more details about crash dumps.
Usage of bzImage for capturing the crash dump is recommended as