fstab

# top mount point
/shared                /shared       none    bind,unbindable,shared  0 0

# virtual machines
/lxc/c1                /shared/c1    none    bind    0 0
/lxc/c2                /shared/c2    none    bind    0 0
/lxc/c3                /shared/c3    none    bind    0 0

/home                  /shared/home  none    bind    0 0

remount-shared.sh

#!/bin/bash

mnts="c1 c2 c3 home"

for i in $mnts; do
        umount /shared/$i
done

for i in $mnts; do
        mount /shared/$i
done

ls /shared/*

exit 0

sharing mounts to and between lxc containers

This is based on: https://s3hh.wordpress.com/2011/09/22/sharing-mounts-with-a-container/

This is for a trusted environment only.
The lxc rootfs for each container is located under: /shared/c?

Setup:
1. mkdir /shared /shared/c{1,2,3}
2. add entries to /etc/fstab (see file excerpt)
3. start the lxc's
4. run remount-shared.sh on the host if the mount points are missing inside the lxc's

Step 4 appears to be required because the lxc umounts the directories during startup (possibly related to pivot root)