I have one more thing.
I need to add a disk into LXC (privileged) but the ownership of the mountpoint is always root:root. How can I set the mountpoint to be owned by other user and group?
What I am doing is to place mysql databases onto other disk then rootdisk.
So I added mountpoint /var/lib/mysql but mysql directory is root:root. I can chown it of course but after containers' restart it's root:root again.