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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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