LVM on secondary LUKS device
Today I ran into a problem when I set up my new SSD. I have two fully encrypted disks (one SSD and one HDD) and two volume groups (VGs) on top. Each disk has its own VG. I thought about the following partition scheme. sda is the SSD and sdb the HDD:
/dev/sda2 → LUKS → /dev/mapper/luksmain /dev/sdb1 → LUKS → /dev/mapper/luksdata /dev/mapper/luksmain → LVM → /dev/mapper/main /dev/mapper/luksdata → LVM → /dev/mapper/data
And from these block devices set up the following file systems:
/dev/mapper/main-root / /dev/sda1 /boot /dev/mapper/main-home /home /dev/mapper/data-var /var /dev/mapper/data-music /home/Music /dev/mapper/data-videos /home/Videos /dev/mapper/main-mysql /var/lib/mysql
As one can see, the logical volume (LV) data-var is required by the system. It contains e.g. the logs or the package cache.
To use it during startup, enable the lvm-on-luks systemd service:
systemctl enable lvm-on-luks.service