ubuntu@ubuntu:~$ sudo mount /dev/sda4 /mnt
ubuntu@ubuntu:~$ sudo btrfs subvolume set-default 5 /mnt
ubuntu@ubuntu:~$ sudo mount --bind /dev /mnt/dev &&
> sudo mount --bind /dev/pts /mnt/dev/pts &&
> sudo mount --bind /proc /mnt/proc &&
> sudo mount --bind /sys /mnt/sys
mount: mount point /mnt/dev does not exist
ubuntu@ubuntu:~$