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SubjectRe: [PATCH] Kdump documentation update for 2.6.20
On Wed, Jan 10, 2007 at 02:45:15PM +0530, Vivek Goyal wrote:
> On Wed, Jan 10, 2007 at 11:07:05AM +0530, Mohan Kumar M wrote:
> > On Tue, Jan 09, 2007 at 08:17:08PM +0530, Vivek Goyal wrote:
> > >
> > > Mohan, Can you please check the correctness of ppc64 specific details.
> > >
> >
> > Vivek,
> >
> > My inputs.
> >
>
> Thanks Mohan. I have updated the document as per your feedback.
>
> Please find attached the latest patch.
>
> Thanks
> Vivek
>
>
> o Kdump documentation update.
> - Update details for using relocatable kernel.
> - Start using kexec-tools-testing release as it is latest and old
> kexec-tools can't load relocatable bzImage file.
> - Also add kdump on ia64 specific details.
>
> Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>

This seems like a great improvement on the existing document.
Lets get this in the tree and make any further changes from there.
I'll send a patch to add the ia64 details shortly.

Signed-off-by: Simon Horman <horms@verge.net.au>

> ---
>
> Documentation/kdump/kdump.txt | 224 ++++++++++++++++++++++++++++--------------
> 1 file changed, 152 insertions(+), 72 deletions(-)
>
> diff -puN Documentation/kdump/kdump.txt~kdump-documentation-update Documentation/kdump/kdump.txt
> --- linux-2.6.20-rc2-mm1-reloc/Documentation/kdump/kdump.txt~kdump-documentation-update 2007-01-08 12:32:55.000000000 +0530
> +++ linux-2.6.20-rc2-mm1-reloc-root/Documentation/kdump/kdump.txt 2007-01-10 14:38:58.000000000 +0530
> @@ -17,7 +17,7 @@ You can use common Linux commands, such
> 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, and ppc64
> +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
> @@ -54,59 +54,64 @@ memory," in two ways:
> Setup and Installation
> ======================
>
> -Install kexec-tools and the Kdump patch
> ----------------------------------------
> +Install kexec-tools
> +-------------------
>
> 1) Login as the root user.
>
> 2) Download the kexec-tools user-space package from the following URL:
>
> - http://www.xmission.com/~ebiederm/files/kexec/kexec-tools-1.101.tar.gz
> +http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/kexec-tools-testing-20061214.tar.gz
>
> -3) Unpack the tarball with the tar command, as follows:
> -
> - tar xvpzf kexec-tools-1.101.tar.gz
> -
> -4) Download the latest consolidated Kdump patch from the following URL:
> -
> - http://lse.sourceforge.net/kdump/
> +Note: Latest kexec-tools-testing git tree is available at
>
> - (This location is being used until all the user-space Kdump patches
> - are integrated with the kexec-tools package.)
> +git://git.kernel.org/pub/scm/linux/kernel/git/horms/kexec-tools-testing.git
> +or
> +http://www.kernel.org/git/?p=linux/kernel/git/horms/kexec-tools-testing.git;a=summary
>
> -5) Change to the kexec-tools-1.101 directory, as follows:
> +3) Unpack the tarball with the tar command, as follows:
>
> - cd kexec-tools-1.101
> + tar xvpzf kexec-tools-testing-20061214.tar.gz
>
> -6) Apply the consolidated patch to the kexec-tools-1.101 source tree
> - with the patch command, as follows. (Modify the path to the downloaded
> - patch as necessary.)
> +4) Change to the kexec-tools-1.101 directory, as follows:
>
> - patch -p1 < /path-to-kdump-patch/kexec-tools-1.101-kdump.patch
> + cd kexec-tools-testing-20061214
>
> -7) Configure the package, as follows:
> +5) Configure the package, as follows:
>
> ./configure
>
> -8) Compile the package, as follows:
> +6) Compile the package, as follows:
>
> make
>
> -9) Install the package, as follows:
> +7) Install the package, as follows:
>
> make install
>
>
> -Download and build the system and dump-capture kernels
> -------------------------------------------------------
> +Build the system and dump-capture kernels
> +-----------------------------------------
> +There are two possible methods of using Kdump.
> +
> +1) Build a separate custom dump-capture kernel for capturing the
> + kernel core dump.
> +
> +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.
> +
> +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
> +at the same time one might want to build a custom dump capture kernel
> +suitable to his needs.
>
> -Download the mainline (vanilla) kernel source code (2.6.13-rc1 or newer)
> -from http://www.kernel.org. Two kernels must be built: a system kernel
> -and a dump-capture kernel. Use the following steps to configure these
> -kernels with the necessary kexec and Kdump features:
> +Following are the configuration setting required for system and
> +dump-capture kernels for enabling kdump support.
>
> -System kernel
> --------------
> +System kernel config options
> +----------------------------
>
> 1) Enable "kexec system call" in "Processor type and features."
>
> @@ -132,88 +137,160 @@ System kernel
> analysis tools require a vmlinux with debug symbols in order to read
> and analyze a dump file.
>
> -4) Make and install the kernel and its modules. Update the boot loader
> - (such as grub, yaboot, or lilo) configuration files as necessary.
> +Dump-capture kernel config options (Arch Independent)
> +-----------------------------------------------------
>
> -5) Boot the system kernel with the boot parameter "crashkernel=Y@X",
> - where Y specifies how much memory to reserve for the dump-capture kernel
> - and X specifies the beginning of this reserved memory. For example,
> - "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
> - starting at physical address 0x01000000 for the dump-capture kernel.
> -
> - On x86 and x86_64, use "crashkernel=64M@16M".
> -
> - On ppc64, use "crashkernel=128M@32M".
> +1) Enable "kernel crash dumps" support under "Processor type and
> + features":
>
> + CONFIG_CRASH_DUMP=y
>
> -The dump-capture kernel
> ------------------------
> +2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems".
>
> -1) Under "General setup," append "-kdump" to the current string in
> - "Local version."
> + CONFIG_PROC_VMCORE=y
> + (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
>
> -2) On x86, enable high memory support under "Processor type and
> +Dump-capture kernel config options (Arch Dependent, i386)
> +--------------------------------------------------------
> +1) On x86, enable high memory support under "Processor type and
> features":
>
> CONFIG_HIGHMEM64G=y
> or
> CONFIG_HIGHMEM4G
>
> -3) On x86 and x86_64, disable symmetric multi-processing support
> +2) On x86 and x86_64, disable symmetric multi-processing support
> under "Processor type and features":
>
> 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
> Kernel".)
>
> -4) On ppc64, disable NUMA support and enable EMBEDDED support:
> +3) If one wants to build and use a relocatable kernel,
> + Enable "Build a relocatable kernel" support under "Processor type and
> + features"
>
> - CONFIG_NUMA=n
> - CONFIG_EMBEDDED=y
> - CONFIG_EEH=N for the dump-capture kernel
> + CONFIG_RELOCATABLE=y
>
> -5) Enable "kernel crash dumps" support under "Processor type and
> - features":
> +4) 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. A suitable value depends upon
> + whether kernel is relocatable or not.
>
> - CONFIG_CRASH_DUMP=y
> + If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
> + This will compile the kernel for physical address 1MB, but given the fact
> + kernel is relocatable, it can be run from any physical address hence
> + kexec boot loader will load it in memory region reserved for dump-capture
> + kernel.
> +
> + Otherwise it should be the start of memory region reserved for
> + second kernel using boot parameter "crashkernel=Y@X". Here X is
> + start of memory region reserved for dump-capture kernel.
> + Generally X is 16MB (0x1000000). So you can set
> + CONFIG_PHYSICAL_START=0x1000000
> +
> +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)
> +----------------------------------------------------------
> +1) On x86 and x86_64, disable symmetric multi-processing support
> + under "Processor type and features":
> +
> + CONFIG_SMP=n
>
> -6) Use a suitable value for "Physical address where the kernel is
> + (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 discussed above.
> + parameter.
>
> - On x86 and x86_64, use "CONFIG_PHYSICAL_START=0x1000000".
> + For x86_64, normally "CONFIG_PHYSICAL_START=0x1000000".
>
> - On ppc64 the value is automatically set at 32MB when
> - CONFIG_CRASH_DUMP is set.
> +3) Make and install the kernel and its modules. DO NOT add this kernel
> + to the boot loader configuration files.
>
> -6) Optionally enable "/proc/vmcore support" under "Filesystems" ->
> - "Pseudo filesystems".
> +Dump-capture kernel config options (Arch Dependent, ppc64)
> +----------------------------------------------------------
>
> - CONFIG_PROC_VMCORE=y
> - (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
> -
> -7) 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)
> +
> +
> +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.
> +
> +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
> + and X specifies the beginning of this reserved memory. For example,
> + "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
> + starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
> +
> + On x86 and x86_64, use "crashkernel=64M@16M".
> +
> + On ppc64, use "crashkernel=128M@32M".
>
> Load the Dump-capture Kernel
> ============================
>
> -After booting to the system kernel, load the dump-capture kernel using
> -the following command:
> +After booting to the system kernel, dump-capture kernel needs to be
> +loaded.
> +
> +Based on the architecture and type of image (relocatable or not), one
> +can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
> +of dump-capture kernel. Following is the summary.
> +
> +For i386:
> + - 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:
> + (To be filled)
> +
> +If you are using a uncompressed vmlinux image then use following command
> +to load dump-capture kernel.
>
> - kexec -p <dump-capture-kernel> \
> + kexec -p <dump-capture-kernel-vmlinux-image> \
> --initrd=<initrd-for-dump-capture-kernel> --args-linux \
> - --append="root=<root-dev> init 1 irqpoll"
> + --append="root=<root-dev> <arch-specific-options>"
>
> +If you are using a compressed bzImage/vmlinuz, then use following command
> +to load dump-capture kernel.
>
> -Notes on loading the dump-capture kernel:
> + kexec -p <dump-capture-kernel-bzImage> \
> + --initrd=<initrd-for-dump-capture-kernel> \
> + --append="root=<root-dev> <arch-specific-options>"
> +
> +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 ppc64:
> + "init 1 maxcpus=1 noirqdistrib"
>
> -* <dump-capture-kernel> must be a vmlinux image (that is, an
> - uncompressed ELF image). bzImage does not work at this time.
> +For IA64
> + (To be filled)
> +
> +
> +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
> @@ -231,6 +308,9 @@ Notes on loading the dump-capture kernel
> * "init 1" boots the dump-capture kernel into single-user mode without
> networking. If you want networking, use "init 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
> + kernel or specify maxcpus=1 option while loading dump-capture kernel.
>
> Kernel Panic
> ============
> _

--
Horms
H: http://www.vergenet.net/~horms/
W: http://www.valinux.co.jp/en/

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