Creating a Mirror of an exisiting linux system


Please consider creating a HOWTO vid of creating a RAID 1 using mdadm of an existing linux server installation (Ubuntu Server, Debian Stretch, etc).

For example: a person has the usual system (/dev/sda1 = /boot, /dev/sda2 = swap, /dev/sda3 = /) on a single drive and later decides to mirror the drive onto an identical disk and run the system from the newly created RAID1.