Arg: no mdadm on Ubuntu 18.04.5 Desktop install disk?

[Tom H]

On Sat, Jan 2, 2021 at 10:07 PM Robert Heller <heller at deepsoft.com>
wrote:
>
> Arg! I want to install Ubuntu 18.04.5 on a LVM volume in the LVM
> container on my *existing* CentOS 6.10 system. The LVM container
> is on a software RAID disk (simple mirror set). This *appears*
> not to be possible (?) since the Ubuntu installer is not
> starting/seeing the RAID array and in live mode, mdadm appears
> absent (question: what happens if I try to run apt-get install
> mdadm on a live ISO system?).

You can install mdadm while booted from the disk/stick and use it.