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kexec-kdump-howto: grubby is suggested modifing kernel cmdline

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For reserving a chunk of memory for kdump kernel, args need be
appended to kernel cmdline. For different Arch, different
bootloaders and related config files are used, it's a little
annoying. Using grubby, it can be very easy to append a single
arg to kernel cmdline, and can save words in howto document.

Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: WANG Chao <chaowang@redhat.com>
This commit is contained in:
Baoquan He 2013-06-06 18:16:05 +08:00
parent 5f6dfdf8db
commit 5d73c78c8b
1 changed files with 7 additions and 56 deletions
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63
kexec-kdump-howto.txt
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@ -66,11 +66,14 @@ as your running kernel, and the crash utility:
# yum --enablerepo=\*debuginfo install kernel-debuginfo.$(uname -m) crash
Next up, we need to modify some boot parameters to reserve a chunk of memory for
the capture kernel. For i686 and x86_64, edit /etc/grub.conf, and append
"crashkernel=128M" to the end of your kernel line. Similarly, append the same to
the append line in /etc/yaboot.conf for ppc64. On ia64, edit /etc/elilo.conf,
adding "crashkernel=256M" to the append line for your kernel. Note that the X
the capture kernel. With the help of grubby, it's very easy to append
"crashkernel=128M" to the end of your kernel boot parameters. Note that the X
values are such that X = the amount of memory to reserve for the capture kernel.
And based on arch and system configuration, one might require more than 128M to
be reserved for kdump. One need to experiment and test kdump, if 128M is not
sufficient, try reserving more memory.
# grubby --args="crashkernel=128M" --update-kernel=/boot/vmlinuz-`uname -r`
Note that there is an alternative form in which to specify a crashkernel
memory reservation, in the event that more control is needed over the size and
@ -88,58 +91,6 @@ This line tells kexec to reserve 64M of ram if the system contains between
512M and 2G of physical memory. If the system contains 2G or more of physical
memory, 128M should be reserved.
Examples:
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
# initrd /initrd-version.img
#boot=/dev/hda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Red Hat Enterprise Linux (2.6.18-8.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-8.el5 ro root=/dev/VolGroup00/LogVol00
initrd /initrd-2.6.18-8.el5.img
# cat /etc/yaboot.conf
# yaboot.conf generated by anaconda
boot=/dev/sda1
init-message=Welcome to Red Hat Enterprise Linux!\nHit <TAB> for boot options
partition=2
timeout=80
install=/usr/lib/yaboot/yaboot
delay=5
enablecdboot
enableofboot
enablenetboot
nonvram
fstype=raw
image=/vmlinuz-2.6.17-1.2621.el5
label=linux read-only
initrd=/initrd-2.6.17-1.2621.el5.img
append="root=LABEL=/ crashkernel=128M"
# cat /etc/elilo.conf
prompt
timeout=20
default=2.6.17-1.2621.el5
relocatable
image=vmlinuz-2.6.17-1.2621.el5
label=2.6.17-1.2621.el5
initrd=initrd-2.6.17-1.2621.el5.img read-only
append="-- root=LABEL=/ crashkernel=256M"
After making said changes, reboot your system, so that the X MB of memory is
left untouched by the normal system, reserved for the capture kernel. Take note
that the output of 'free -m' will show X MB less memory than without this