Log into the container and create an empty directory, this will be the mount point
Log out and stop the container.
Open to your container’s config file
For regular LXC containers: /var/lib/lxc/mycontainer/config
For unprivileged LXC containers: $HOME/.local/share/lxc/mycontainer/config
Add a new line above the lxc.mount directive, that follows the format below. Substitute proper paths as necessary:
lxc.mount.entry = /path/to/folder/on/host /path/to/mount/point none bind 0 0
Both of these paths are relative to the host machine.
Location of the root fs in the container can be found at:
For regular LXC containers: /var/lib/lxc/mycontainer/rootfs/
For unprivileged LXC containers: $HOME/.local/share/lxc/mycontainer/rootfs
Note: If the host’s user does not exist in the container, the container will still be mounted, but with nobody:nogroup as the owner. This may not be a problem unless you need to write to these files, in which case you’ll need to give everybody write permission to that folder. (i.e. chmod -R go+w /folder/to/share)
Example
I want to share /home/julianlam/foobar to my unprivileged container bazquux. In bazquux, I want this folder to be found at /mnt/baz.
In the container:
$ cd /mnt
$ sudo mkdir baz
$ logout
In the host, I will add the following line above lxc-mount in /home/julianlam/.local/share/lxc/bazquux/config:
lxc.mount.entry = /home/julianlam/foobar /home/julian/.local/share/lxc/bazquux/rootfs/mnt/baz none bind 0 0
Then
$ lxc-start -n bazquux -d