MOUNT FOLDER SHARED WITH THE HOST

# data folder on the host machine
/mnt/raiddisk/bookstack
chown www-data:www-data bookstack

# in lxc container configuration file
/etc/pve/lxc/<lxc_id>.conf

mp0: /mnt/raiddisk/bookstack,mp=/mnt/bookstack,replicate=0
lxc.idmap: u 0 100000 1
lxc.idmap: g 0 100000 1
lxc.idmap: u 1 33 1
lxc.idmap: g 1 33 1
lxc.idmap: u 2 100002 65533
lxc.idmap: g 2 100002 65533