mjhjmtu

I want to use the root directory as the base of a couple of containers which I wanted to keep in my /home.

But the problem is, I chose Guided Partitioning with the Separate /home partition option on the Debian installer, then formatted both of the partitions to Btrfs.

$ lsblk 
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 931.5G 0 disk 
├─sda1 8:1 0 28G 0 part /
├─sda2 8:2 0 1K 0 part 
├─sda5 8:5 0 11G 0 part [SWAP]
└─sda6 8:6 0 892.6G 0 part /home

My root and /home aren't subvols in the same partition, but separate Btrfs partitions.

Now, I tried to snapshot root into my /home and of course it didn't work as I Googled around and figured out why.

$ sudo btrfs subvolume snapshot / Downloads/test
Create a snapshot of '/' in 'Downloads/test'
ERROR: cannot snapshot '/': Invalid cross-device link

I also tried to use overlay to get a virtual copy of the root, but that didn't work out so well, either:

$ sudo mount -t overlay -o lowerdir=/ overlay Downloads/test
mount: /home/ontoki/Downloads/test: wrong fs type, bad option, bad superblock on overlay, missing codepage or helper program, or other error.

How do I mount btrfs volumes across different partitions, and is it possible to make merged directory like overlay allows?