Features/NewMkdumprd

New mkdumprd for kdump

Summary

This is a replacement for mkdumprd of kexec-tools, to switch to dracut to generate the initrd for kdump kernel.

This feature was postponed in Fedora 16, because some feature needed in dracut was not done. Now the latest dracut has the thing we need, --mount, although it is still experimental.

Owner

• Name: Cong Wang and Dave Young

• Email: <xiyou.wangcong at gmail.com> or <amwang at redhat dot com> / ruyang@redhat.com

Current status

• Targeted release: Fedora 17
• Last updated: 2012-02-22
• Percentage of completion: 90%

Working:

• Dump to root filesystem
• Dump to local filesystem (including multiple targets)
• Part of configs in /etc/kdump.conf work:
  • <fs type> <partition>
  • path <path>
  • core_collector <core_collector>
  • extra_bins <bins>
  • extra_modules <module(s)>
  • default <reboot | halt | shell>
• Obsolete:
  • disk_timeout <seconds>
  • link_delay <seconds>
  • options <module> <option list>
• Dump to remote host via ssh
  • Depends on dracut ssh-client module (ruyang)
• Dump to remote host via nfs
  • Depends on dracut nfs, network module and --mount

TODO:

• Dump to raw block device
• Implement full functionality of /etc/kdump.conf
• Dump to multiple targets

Detailed Description

Currently in kexec-tools we use our own /sbin/mkdumprd to generate an initrd for kdump kernel. However, due to the natural complexity of making a new initrd, we have lots of burdens to maintain the mkdumprd code, we decide to switch to using dracut to generate kdump initrd. And hopefully, we can provide a distro-independent mkdumprd to upstream, as dracut itself is cross-distribution.

Benefit to Fedora

The main source of kexec-tools bugs is in mkdumprd, with this change, hopefully we will reduce the number of bugs of kexec-tools.

Scope

All functionality of /sbin/mkdumprd has to be implemented and tested in this new mkdumprd.

How To Test

Enable some of the following config lines in /etc/kdump.conf

• Dump to local file system

ext3 LABEL=/boot

ext3 /dev/sda1

ext4 UUID=03138356-5e61-4ab3-b58e-27507ac41937

• Dump to remote machines

net my.server.com:/path

net user@remote.server.com

• Dump to raw block device

raw /dev/sda5

• Other configs

core_collector makedumpfile -c --message-level 1

core_collector cp

kdump_post /var/crash/scripts/kdump-post.sh

extra_bins /bin/cp

disk_timeout 30

extra_modules gfs2

options modulename options

default shell/reboot/shutdown

Trigger a crash and see if the vmcore is dumped to the right place.

User Experience

Users should not notice the replacement, because we plan to provide full backward compatibility.

Dependencies

Dracut

Contingency Plan

Fallback to old /sbin/mkdumprd.

Documentation

• kdump.conf: http://www.linuxcertif.com/man/5/kdump.conf/

Release Notes

• /sbin/mkdumprd has been replaced by new code, which uses dracut to generate the initrd for kdump kernel.

Comments and Discussion

https://fedoraproject.org/wiki/Talk:Features/NewMkdumprd