Proxmox: Mount USB disk to VZ or LXC container

First check what is the number of VZ container you want to mount disk to:

vzlist

Look at CTID number.

Then mount disk under folder on host (it's called HN in documentation):

mount /dev/sdb3 /mnt/usb

So partition sdb3 is now mounted in Proxmox host under /mnt/usb.

If the disk has GPT do this:

parted /dev/sdb print

and then choose right partition number.

Next bind directory to VZ container:

mount --bind /mnt/usb/ /var/lib/vz/root/119/mnt/usb/

Now, disk is bind-mounted to /mnt/usb folder inside the debian9.pws machine which has CTID number 119.

In LXC:

Mount external disk to some directory:

mount /dev/sdb3 /mnt/sdb3

then shutdown container and mount directory /mnt/sdb3 under /shared directory- inside container:

pct set 100 -mp0 /mnt/sdb1,mp=/shared