Ubuntu Manpage: kdump-tools.conf - configuration file for the kdump-tools init script

Provided by: kdump-tools_1.8ubuntu1_amd64

NAME

       kdump-tools.conf - configuration file for the kdump-tools init script

SYNOPSIS

       /etc/default/kdump-tools

DESCRIPTION

       kdump-tools  manages  the kdump feature of the Linux kernel.  The /etc/default/kdump-tools
       file contains local configuration settings of kdump.

       This file is sourced into a shell script, so it's format should be consistent  with  shell
       scripting.

OPTIONS

USE_KDUMP
Controls whether or not kdump-tools will take any action. If not set or 0, the
kdump-tools init script will not run.

KDUMP_KERNEL
A full pathname to a kdump kernel (the kernel that is kexec'd at crash time in a
reserved memory area, exposing the old kernel's memory for dumping). If not set,
kdump-config will use the boot kernel as the kdump kernel if it is relocatable;
otherwise you must set KDUMP_KERNEL in order for kdump-tools to work.

KDUMP_INITRD
A full pathname to the kdump initrd (if used). If KDUMP_KERNEL is set and
KDUMP_INITRD is not set, a warning message will be printed, and an initrd will not
be used.

KDUMP_COREDIR
Full path to a directory where the vmcore will be saved. Date stamped
subdirectories are created each time a vmcore file is processed. If not set,
/var/crash will be used.

KDUMP_FAIL_CMD
This variable specifies a command to run if the vmcore save fails. If not set, no
special action is taken.

KDUMP_DUMP_DMESG
This variable controls if the dmesg buffer is dumped. If not set or set to 1, the
dmesg buffer is dumped. If set to 0, the dmesg buffer is not dumped.

KDUMP_NUM_DUMPS
This variable specifies how many dump files should be kept on the local machine.
If not set or set to 0, no special action is taken. If set to >1 and there are too
many dump files on the machine, older dumps are removed. The cleanup action is only
taken after a successful dump. This variable is ignored if remote dumping is
enabled.

MAKEDUMP_ARGS
Extra arguments passed to makedumpfile(8). If not set, “-c -d 31” will be used.
This tells makedumpfile to use compression, and reduce the corefile to in-use
kernel pages only. See makedumpfile(8) for details.

KDUMP_KEXEC_ARGS
Additional arguments to the kexec command used to load the kdump kernel.

KDUMP_CMDLINE
Normally, the current kernel commandline is obtained from /proc/cmdline. Set this
variable to override /proc/cmdline.

KDUMP_CMDLINE_APPEND
Additional arguments to append to the command line for the kdump kernel. If not
set, “reset_devices systemd.unit=kdump-tools-dump.service nr_cpus=1 irqpoll nousb”
will be used.

SSH username and hostname of the remote server that will receive the dump and dmesg
files. username@hostname format must be used.

SSH_KEY
Full path of the ssh private key to be used to login to the remote server. Use
“kdump-config propagate” to send the public key to the remote server. If not set,
the default /root/.ssh/kdump_id_rsa will be used

HOSTTAG
Select if hostname of IP address will be used as a prefix to the timestamped
directory when sending files to the remote server. If not set, “ip” will be used.

NFS Hostname and mount point of the NFS server configured to receive the crash dump.
The syntax must be HOSTNAME:MOUNTPOINT (e.g. remote:/var/crash )

USAGE

kdump-tools is as automated as can be at this point but there are some prerequisites to
using it. Additionally, some manual configuration is still required.

By default, kernel dumps are stored locally on the system. kdump-tools can be configured
to store the kernel dumps on a remote server accessible through the network.

Manual Configuration
1. USE_KDUMP is set to 0 by default. To enable kdump-tools, edit the
/etc/default/kdump-tools configuration file and set USE_KDUMP=1.

2. Kernel Command line parameters - the kernel must be booted with a crashkernel=
command line parameter. Some example crashkernel parameters:
ia64: crashkernel=384M
x86: crashkernel=128M
x86_64: crashkernel=256M

Some users may also want to add nmi_watchdog=1 on certain systems. The nmi
watchdog will cause the kernel to panic (and kdump) if a system hang is detected.

The kernel command line parameter is generally set in one of these files:
/etc/default/grub, /boot/grub/menu.lst, /etc/elilo.conf, or /etc/lilo.conf. If the
command line parameter is changed, a reboot is required in order for it to take
effect.

3. Architectural considerations

A) x86 && PAE && memory > 4 Gigabytes - use KDUMP_KEXEC_ARGS="--elf64-core-
headers"

B) x86 and x86_64 - Some systems can take advantage of the nmi watchdog. Add
nmi_watchdog=1 to the boot commandline to turn on the watchdog. The nmi
interrupt will call panic if activated.

C) ia64 - Some systems may need KDUMP_KEXEC_ARGS="--noio". Use this if the
system hangs after a panic, but before the kdump kernel begins to boot.

Networked kernel dump Configuration
1. Either use SSH or NFS to choose which protocol to use to remotely access the target
server.

2 For SSH username@hostname needs to be provided along with an appropriate SSH_KEY
definition or use “kdump-config propagate” to propagate a new default ssh key.

3 For NFS the remote server name must be provided along with the directory where
files are to be copied.

Prerequisites
1. Boot Kernel Configuration - The boot kernel must be configured with CONFIG_KEXEC=y
and, if it is also to be used as the kdump kernel, CONFIG_CRASHDUMP=y.

For ia64, only makedumpfile level 1 will work if the memory model selected is
CONFIG_DISCONTIG. CONFIG_SPARSEMEM is recommended instead.

2. Kdump Kernel Configuration - The kdump kernel must be relocated or relocatable.
ia64 is relocatable by default, but x86, x86_64, and powerpc must be built with
CONFIG_RELOCATABLE=y. Other architectures may require a predermined start location
via CONFIG_PHYSICAL_START. If the boot kernel is relocatable, kdump-tools will
automatically use that kernel. Otherwise, a relocatable or relocated kernel will
need to be provided. The kdump kernel can be specified in the /etc/default/kdump-
tools file. Set the KDUMP_KERNEL variable and if necessary the KDUMP_INITRD
variable to point to the provided kernel and its initrd.

The kdump kernel must be configured with: CONFIG_CRASH_DUMP=y

SYSCTLS

       Currently  kdump-tools automatically sets the kernel sysctl for panic on oops, in order to
       collect a dump in this case. If the users want more panic triggers, like panic on OOM,  or
       when  a  NMI  is  detected, it's recommended that they edit the sysctl configuration files
       (/etc/sysctl.conf or files on /etc/sysctl.d) in order to do so, and/or  apply  the  sysctl
       settings with sysctl tool.

   Sysctl handling *during a kdump*
       kdump-tools  allows  users  to  configure  sysctls overrides on kdump environment; this is
       specially useful to prevent sysctls from the regular  boot  to  mess  with  the  resource-
       impaired kdump environment.

       The  mechanism  is restricted to kdump boot and will not affect regular boots. In order to
       add overrides, user should edit the file /etc/kdump/sysctl.conf.

       By default, hugepages overrides are set and is highly recommended  to  keep  them  in  the
       file, to prevent kdump out-of-memory conditions.

EXAMPLES

       Use this option on x86 systems with PAE and more than 4 gig of memory:
              KDUMP_KEXEC_ARGS="--elf64-core-headers"

       This option starts a shell if kdump-tools cannot save the vmcore file:
              KDUMP_FAIL_CMD="/bin/bash; reboot -f"

FILES

       /etc/init.d/kdump-tools  an  init  script  to automatically load a kdump kernel, or save a
                                vmcore and reboot.

       /etc/default/kdump-tools the kdump-tools configuration file

       /etc/kdump/sysctl.conf   kdump-tools sysctl override file

       /var/crash/kernel_link   a link to the current debug kernel

       /var/crash/kexec_cmd     the last kexec_cmd executed by kdump-config

DIAGNOSTICS

       See kdump-config(8) for explanations of various error messages.

AUTHOR

       Terry Loftin <terry.loftin@hp.com>