Reducing size of container LV
Step One - CONFIRM volume name and path
pct list
pct stop <container id number>
lvdisplay | grep "LV Path\|LV Size"
Step 2 - Resize file system and logical volume
resize2fs /dev/pve/vm-999-disk-0 10G
lvreduce -L 10G /dev/pve/vm-999-disk-0
Step 3 - Edit container conf
nano /etc/pve/lxc/<container id>.conf
rootfs: local-lvm:vm-999-disk-0,size=32G >> rootfs: local-lvm:vm-999-disk-0,size=10G
Step 4 - Confirm new disk size
pct start <container id>
pct enter <container id>
df -h