User:NeddySeagoon/Root Inside LVM On Raid

Overview
There is nothing new in Root Inside LVM On Raid, so why another document?

Conventional wisdom says to use an an initrd to start the raid, then poke about inside the raid to bring up LVM so the kernel can actually see the root logical volume. That's well documented elsewhere.

Lets do it without an initrd.

"In theory there is no difference between theory and practice - in practice there is"

This process is for users that have some experience of managing both raid sets and logical volumes.

Consider it like driving the Monte Carlo rally. You must have participated as a navigator before you can drive it. Accordingly, the instructions are somewhat abbreviated.

Making The Raid Set
As there is no initrd, we will use kernel raid autoassembly.

That's conventional but raid superblock vers=0.90 must be used.

Making the Volume Group and Logical Volumes
As the kernel is going to poke around for vg-root, there are some constraints on how the physical volume is constructed. This proof of concept will use linear on top of raid. It will be a single /dev/mdX.

Keep that in mind. Everything else is usual LVM commands.

The Kernel
The kernel needs to support the raid level(s) in use, built in. The required device mapper options, built in. In particular, DM_INIT, as this allows the kernel to parse the kernel command line to know how to find root.