This is a very useful feature for access to the host file system from an LXC Container:
Bind Mount Points
Bind mounts allow you to access arbitrary directories from your Proxmox VE host inside a container. Some potential use cases are:
Accessing your home directory in the guest
Accessing an USB device directory in the guest
Accessing an NFS mount from the host in the guest
Bind mounts are considered to not be managed by the storage subsystem, so you cannot make snapshots or deal with quotas from inside the container. With unprivileged containers you might run into permission problems caused by the user mapping and cannot use ACLs.
Note The contents of bind mount points are not backed up when using vzdump.
Warning For security reasons, bind mounts should only be established using source directories especially reserved for this purpose, e.g., a directory hierarchy under /mnt/bindmounts. Never bind mount system directories like /, /var or /etc into a container - this poses a great security risk.
Note The bind mount source path must not contain any symlinks.
For example, to make the directory /mnt/bindmounts/shared accessible in the container with ID 100 under the path /shared, use a configuration line like mp0: /mnt/bindmounts/shared,mp=/shared in /etc/pve/lxc/100.conf. Alternatively, use pct set 100 -mp0 /mnt/bindmounts/shared,mp=/shared to achieve the same result.