local fs = require "nixio.fs"
local opkg = require "luci.model.ipkg"

local st = fs.statvfs(opkg.overlay_root())
local blocks = st.blockss or 0
local bfree = st.bfree or 0
local used = ((blocks - bfree) / blocks)

return math.floor(used * 1000 + 0.5) / 1000