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OLVM: Potential KVM host boot failure if / root File System on LVM Logical Volume (Doc ID 2899132.1)

Last updated on SEPTEMBER 28, 2022

Applies to:

Linux OS - Version Oracle Linux 7.5 with Unbreakable Enterprise Kernel [4.14.35] and later
Linux x86-64

Purpose

The dracut kernel command line won't accept LVM by uuid - a unique identifier, but with label - a none unique identifier.
LVM
rd.lvm=0
disable LVM detection

rd.lvm.vg=<volume group name>
only activate all logical volumes in the the volume groups
with the given name. rd.lvm.vg can be specified multiple
times on the kernel command line.

rd.lvm.lv=<volume group name>/<logical volume name>
only activate the logical volumes with the given name.
rd.lvm.lv can be specified multiple times on the kernel
command line.

rd.lvm.conf=0
remove any /etc/lvm/lvm.conf, which may exist in the
initramfs

So when install Oracle Linux for KVM host, if leave it with default LVM VG and LV names, it will have ol as VG name, and root & swap for LV names, etc:
/dev/mapper/ol-root
/dev/mapper/ol-swap

 

Then /etc/default/grub will have info like:
...
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=ol/root rd.lvm.lv=ol/swap rhgb quiet"
...

 

If later, any Oracle Linux VM on this KVM has its / root disk installed on a direct LUN also leaving with default LVM VG and LV names, there is a chance during next boot up of KVM host, during Initramfs stage it might activate the wrong disk, hence KVM host boot failure.

 

 

Details

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