1704064885
Kdump service starts too late, so early crashes will have no chance to get kdump kernel booting, this will cause crash information to be lost. It is necessary to add a dracut module in order to load crash kernel and initramfs as early as possible. You can provide "rd.early kdump" in grub commandline to enable, then the early kdump will load those files like the normal kdump, which is disabled by default. For the normal kdump service, it can check whether the early kdump has loaded the crash kernel and initramfs. It has no conflict with the early kdump. If you rebuild the new initramfs for early kdump, the new initramfs size will become large, because it will put the vmlinuz and kdump initramfs into the new initramfs. In addition, early kdump doesn't support fadump. Signed-off-by: Lianbo Jiang <lijiang@redhat.com> Reviewed-by: Kazuhito Hagio <khagio@redhat.com> Acked-by: Dave Young <dyoung@redhat.com>
55 lines
2.0 KiB
Plaintext
55 lines
2.0 KiB
Plaintext
Early Kdump HOWTO
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Introduction
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Kdump service starts too late, so early crashes will have no chance to get
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kdump kernel booting, this will cause crash information to be lost. It is
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necessary to add a dracut module in order to load crash kernel and initramfs
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as early as possible. You can provide "rd.earlykdump" in grub commandline
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to enable, then the early kdump will load those files like the normal kdump,
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which is disabled by default.
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For the normal kdump service, it can check whether the early kdump has loaded
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the crash kernel and initramfs. It has no conflict with the early kdump.
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How to configure early kdump:
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We assume if you're reading this document, you should already have kexec-tools
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installed.
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You can rebuild the initramfs with earlykdump support with below steps:
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1. start kdump service to make sure kdump initramfs is created.
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# systemctl start kdump
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2. rebuild system initramfs with earlykdump support.
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# dracut --add earlykdump
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3. add rd.earlykdump in grub kernel command line.
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Note: earlykdump initramfs size will be large because it includes vmlinuz and
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kdump initramfs. And for step 2 if you are sure to overwrite system initramfs
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you can backup the original initramfs and use "--force" option.
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After making said changes, reboot your system to take effect. Of course, if you
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want to disable early kdump, you can simply remove "rd.earlykdump" from kernel
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boot parameters in grub, and reboot system like above.
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Once the boot is completed, you can check the status of the early kdump support
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on the command prompt:
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# journalctl -x|grep early-kdump
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Then, you will see some useful logs, for exapmle:
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1. if early kdump is successful.
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Mar 09 09:57:56 localhost.localdomain dracut-cmdline[190]: early-kdump is enabled.
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Mar 09 09:57:56 localhost.localdomain dracut-cmdline[190]: kexec: loaded early-
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kdump kernel
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2. if early kdump is disabled.
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Mar 09 10:02:47 localhost.localdomain dracut-cmdline[189]: early-kdump is disabled.
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Limitation
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At present, early kdump doesn't support fadump.
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