diff --git a/ngcp/.luacheckrc b/ngcp/.luacheckrc
index 80ee3c9..cd11ffc 100644
--- a/ngcp/.luacheckrc
+++ b/ngcp/.luacheckrc
@@ -1 +1,2 @@
 globals = {'sr', '_ENV'}
+ignore = { 'NGCP.*', '212' }
\ No newline at end of file
diff --git a/ngcp/avp.lua b/ngcp/avp.lua
index 0cba854..63eec83 100644
--- a/ngcp/avp.lua
+++ b/ngcp/avp.lua
@@ -27,20 +27,17 @@ NGCPAvp_MT = {
 
     function NGCPAvp:new(id)
         local t = { id = "$avp(s:" .. id .. ")" }
-        NGCPAvp_MT.__call = function(t, value)
+        NGCPAvp_MT.__call = function(s, value)
             if not value then
-                --print(table.tostring(sr.pv.vars))
-                --print(t.id)
-                return sr.pv.get(t.id)
+                return sr.pv.get(s.id)
             elseif type(value) == "table" then
-                local i, v
                 for i = #value, 1, -1 do
-                    t(value[i])
+                    s(value[i])
                 end
             elseif type(value) == "number" then
-                sr.pv.seti(t.id, value)
+                sr.pv.seti(s.id, value)
             elseif type(value) == "string" then
-                sr.pv.sets(t.id, value)
+                sr.pv.sets(s.id, value)
             else
                 error("value is not a number or string")
             end
@@ -48,9 +45,9 @@ NGCPAvp_MT = {
         function t.all()
             return sr.pv.get("$(avp(" .. id .. ")[*])")
         end
-        NGCPAvp_MT.__tostring = function(t)
-            local value = sr.pv.get(t.id)
-            return string.format("%s:%s", t.id, tostring(value))
+        NGCPAvp_MT.__tostring = function(s)
+            local value = sr.pv.get(s.id)
+            return string.format("%s:%s", s.id, tostring(value))
         end
         return setmetatable( t, NGCPAvp_MT )
     end
diff --git a/ngcp/config.lua b/ngcp/config.lua
index f66207e..d533e8f 100644
--- a/ngcp/config.lua
+++ b/ngcp/config.lua
@@ -20,6 +20,7 @@
 
 -- load drivers
 local driver = require "luasql.mysql"
+-- luacheck: ignore luasql
 if not luasql then
     luasql = driver
 end
@@ -77,8 +78,8 @@ NGCPConfig_MT = { __index = NGCPConfig }
 
     local function check_connection(c)
         local cur = c:execute("SELECT 1")
-        local row = cur:fetch()
         local result = false
+        cur:fetch()
         if cur:numrows() == 1 then
             result = true
         end
@@ -91,7 +92,7 @@ NGCPConfig_MT = { __index = NGCPConfig }
             self.env = assert (luasql.mysql())
         end
         if self.con then
-            local ok,err = pcall(check_connection, self.con)
+            local ok,_ = pcall(check_connection, self.con)
             if not ok then
                 self.con = nil
                 sr.log("dbg", "lost database connection. Reconnecting")
@@ -106,7 +107,6 @@ NGCPConfig_MT = { __index = NGCPConfig }
     end
 
     function NGCPConfig:get_defaults(vtype)
-        local k,v
         local defs = {}
 
         if self.default[vtype] then
diff --git a/ngcp/cp.lua b/ngcp/cp.lua
index 62c7e31..22bbf53 100644
--- a/ngcp/cp.lua
+++ b/ngcp/cp.lua
@@ -27,7 +27,7 @@ NGCPContractPrefs = {
 NGCPContractPrefs_MT = { __index = NGCPContractPrefs }
 
 NGCPContractPrefs_MT.__tostring = function ()
-        local output = ''
+        local output
         local xavp = NGCPXAvp:new('caller','contract_prefs')
         output = string.format("caller_contract_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','contract_prefs')
@@ -59,10 +59,9 @@ NGCPContractPrefs_MT.__tostring = function ()
         return NGCPContractPrefs._load(self,"callee",contract)
     end
 
-    function NGCPContractPrefs:_defaults(level)
+    function NGCPContractPrefs:_defaults(_)
         local defaults = self.config:get_defaults('contract')
         local keys = {}
-        local k,_
 
         if defaults then
             for k,_ in pairs(defaults) do
@@ -80,7 +79,6 @@ NGCPContractPrefs_MT.__tostring = function ()
         local keys
         local result = {}
         local row = cur:fetch({}, "a")
-        local k,v
         local xavp
 
         keys, defaults = self:_defaults(level)
diff --git a/ngcp/dlgcnt.lua b/ngcp/dlgcnt.lua
index 159b10f..3816ddb 100644
--- a/ngcp/dlgcnt.lua
+++ b/ngcp/dlgcnt.lua
@@ -63,7 +63,7 @@ end
 
     function NGCPDlgCounters._test_connection(client)
         if not client then return nil end
-        local ok, err = pcall(client.ping, client);
+        local ok, _ = pcall(client.ping, client);
         return ok
     end
 
diff --git a/ngcp/dlglist.lua b/ngcp/dlglist.lua
index d1c4b8b..d4c388d 100644
--- a/ngcp/dlglist.lua
+++ b/ngcp/dlglist.lua
@@ -63,7 +63,7 @@ end
 
     local function _test_connection(client)
         if not client then return nil end
-        local ok, err = pcall(client.ping, client);
+        local ok, _ = pcall(client.ping, client);
         return ok
     end
 
diff --git a/ngcp/dp.lua b/ngcp/dp.lua
index f01a7d6..85b3498 100644
--- a/ngcp/dp.lua
+++ b/ngcp/dp.lua
@@ -27,9 +27,8 @@ NGCPDomainPrefs = {
 NGCPDomainPrefs_MT = { __index = NGCPDomainPrefs }
 
 NGCPDomainPrefs_MT.__tostring = function ()
-        local output = ''
         local xavp = NGCPXAvp:new('caller','dom_prefs')
-        output = string.format("caller_dom_prefs:%s\n", tostring(xavp))
+        local output = string.format("caller_dom_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','dom_prefs')
         output = output .. string.format("callee_dom_prefs:%s\n", tostring(xavp))
         return output
@@ -62,7 +61,6 @@ NGCPDomainPrefs_MT.__tostring = function ()
     function NGCPDomainPrefs:_defaults(level)
         local defaults = self.config:get_defaults('dom')
         local keys = {}
-        local k,_
 
         if defaults then
             for k,_ in pairs(defaults) do
@@ -80,7 +78,6 @@ NGCPDomainPrefs_MT.__tostring = function ()
         local keys
         local result = {}
         local row = cur:fetch({}, "a")
-        local k,v
         local xavp
 
         keys, defaults = self:_defaults(level)
diff --git a/ngcp/ngcp.lua b/ngcp/ngcp.lua
index 8b7d37b..504dfbf 100644
--- a/ngcp/ngcp.lua
+++ b/ngcp/ngcp.lua
@@ -32,9 +32,8 @@ NGCP = {
 NGCP_MT = { __index = NGCP }
 
 NGCP_MT.__tostring = function (t)
-    local k,v
-    output = ''
-    for k,v in pairs(t.prefs) do
+    local output = ''
+    for _,v in pairs(t.prefs) do
         output = output .. tostring(v)
     end
     return output
@@ -62,7 +61,6 @@ end
     end
 
     function NGCP:caller_contract_load(contract)
-        local _,v, xvap
         local keys = self.prefs.contract:caller_load(contract)
 
         self.prefs.real:caller_contract_load(keys)
@@ -70,7 +68,6 @@ end
     end
 
     function NGCP:callee_contract_load(contract)
-        local _,v, xvap
         local keys = self.prefs.contract:callee_load(contract)
 
         self.prefs.real:callee_contract_load(keys)
@@ -78,7 +75,6 @@ end
     end
 
     function NGCP:caller_peer_load(peer)
-        local _,v, xvap
         local keys = self.prefs.peer:caller_load(peer)
 
         self.prefs.real:caller_peer_load(keys)
@@ -86,7 +82,6 @@ end
     end
 
     function NGCP:callee_peer_load(peer)
-        local _,v, xvap
         local keys = self.prefs.peer:callee_load(peer)
 
         self.prefs.real:callee_peer_load(keys)
@@ -94,7 +89,6 @@ end
     end
 
     function NGCP:caller_usr_load(uuid, domain)
-        local _,v
         local keys = {
             domain = self.prefs.dom:caller_load(domain),
             prof   = self.prefs.prof:caller_load(uuid),
@@ -105,13 +99,12 @@ end
         table.merge(unique_keys, keys.user)
 
         self.prefs.real:caller_usr_load(unique_keys)
-        local xavp = NGCPXAvp:new('caller', 'dom')
+        NGCPXAvp:new('caller', 'dom')
 
         return unique_keys
     end
 
     function NGCP:callee_usr_load(uuid, domain)
-        local _,v
         local keys = {
             domain = self.prefs.dom:callee_load(domain),
             prof   = self.prefs.prof:callee_load(uuid),
@@ -127,7 +120,7 @@ end
     end
 
     function NGCP:log_pref(level, vtype)
-        local _,pref,xavp,xavp_log
+        local xavp,xavp_log
 
         if not level then
             level = "dbg"
@@ -157,9 +150,8 @@ end
     end
 
     function NGCP:clean(vtype, group)
-        local _,k,v
         if not group then
-            for k,v in pairs(self.prefs) do
+            for _,v in pairs(self.prefs) do
                 v:clean(vtype)
             end
         else
diff --git a/ngcp/pp.lua b/ngcp/pp.lua
index 8228567..9f4b318 100644
--- a/ngcp/pp.lua
+++ b/ngcp/pp.lua
@@ -27,9 +27,8 @@ NGCPPeerPrefs = {
 NGCPPeerPrefs_MT = { __index = NGCPPeerPrefs }
 
 NGCPPeerPrefs_MT.__tostring = function ()
-        local output = ''
         local xavp = NGCPXAvp:new('caller','peer_prefs')
-        output = string.format("caller_peer_prefs:%s\n", tostring(xavp))
+        local output = string.format("caller_peer_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','peer_prefs')
         output = output .. string.format("callee_peer_prefs:%s\n", tostring(xavp))
         return output
@@ -64,10 +63,9 @@ NGCPPeerPrefs_MT.__tostring = function ()
     function NGCPPeerPrefs:_defaults(level)
         local defaults = self.config:get_defaults('peer')
         local keys = {}
-        local k,_
 
         if defaults then
-            for k,v in pairs(defaults) do
+            for k,_ in pairs(defaults) do
                 table.insert(keys, k)
             end
         end
@@ -82,7 +80,6 @@ NGCPPeerPrefs_MT.__tostring = function ()
         local keys
         local result = {}
         local row = cur:fetch({}, "a")
-        local k,v
         local xavp
 
         keys, defaults = self:_defaults(level)
diff --git a/ngcp/pprof.lua b/ngcp/pprof.lua
index 32d1860..1223330 100644
--- a/ngcp/pprof.lua
+++ b/ngcp/pprof.lua
@@ -28,9 +28,8 @@ NGCPProfilePrefs = {
 NGCPProfilePrefs_MT = { __index = NGCPProfilePrefs }
 
 NGCPProfilePrefs_MT.__tostring = function ()
-        local output = ''
         local xavp = NGCPXAvp:new('caller','prof_prefs')
-        output = string.format("caller_prof_prefs:%s\n", tostring(xavp))
+        local output = string.format("caller_prof_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','prof_prefs')
         output = output .. string.format("callee_prof_prefs:%s\n", tostring(xavp))
         return output
@@ -70,8 +69,6 @@ NGCPProfilePrefs_MT.__tostring = function ()
         local keys = {}
         local result = {}
         local row = cur:fetch({}, "a")
-        local k,v
-        local xavp
 
         if table.size(row) > 0 then
             while table.size(row) > 0 do
@@ -85,7 +82,7 @@ NGCPProfilePrefs_MT.__tostring = function ()
         end
         cur:close()
         if table.size(result) > 0 then
-            xavp = self:xavp(level, result)
+            self:xavp(level, result)
         end
         return keys
     end
diff --git a/ngcp/pref.lua b/ngcp/pref.lua
index f3f3504..614761a 100644
--- a/ngcp/pref.lua
+++ b/ngcp/pref.lua
@@ -27,10 +27,9 @@ NGCPPrefs = {
 NGCPPrefs_MT = { __index = NGCPPrefs }
 
     function NGCPPrefs.init(group)
-        local _,v, xavp
         local levels = {"caller", "callee"}
         for _,v in pairs(levels) do
-            xavp = NGCPXAvp.init(v,group)
+            NGCPXAvp.init(v,group)
         end
     end
 -- class
diff --git a/ngcp/rp.lua b/ngcp/rp.lua
index 10426d5..baf01cc 100644
--- a/ngcp/rp.lua
+++ b/ngcp/rp.lua
@@ -31,9 +31,8 @@ NGCPRealPrefs = {
 NGCPRealPrefs_MT = { __index = NGCPRealPrefs }
 
 NGCPRealPrefs_MT.__tostring = function ()
-        local output = ''
         local xavp = NGCPXAvp:new('caller','real_prefs')
-        output = string.format("caller_real_prefs:%s\n", tostring(xavp))
+        local output = string.format("caller_real_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','real_prefs')
         output = output .. string.format("callee_real_prefs:%s\n", tostring(xavp))
         return output
@@ -71,7 +70,6 @@ NGCPRealPrefs_MT.__tostring = function ()
     end
 
     function NGCPRealPrefs:_contract_load(level, keys)
-        local _,v
         local xavp = {
             contract  = NGCPContractPrefs:xavp(level),
         }
@@ -87,7 +85,6 @@ NGCPRealPrefs_MT.__tostring = function ()
     end
 
     function NGCPRealPrefs:_peer_load(level, keys)
-        local _,v
         local xavp = {
             peer  = NGCPPeerPrefs:xavp(level),
         }
@@ -103,7 +100,6 @@ NGCPRealPrefs_MT.__tostring = function ()
     end
 
     function NGCPRealPrefs:_usr_load(level, keys)
-        local _,v,k
         local xavp = {
             real = NGCPRealPrefs:xavp(level),
             dom  = NGCPDomainPrefs:xavp(level),
diff --git a/ngcp/up.lua b/ngcp/up.lua
index 2778513..3a94810 100644
--- a/ngcp/up.lua
+++ b/ngcp/up.lua
@@ -27,9 +27,8 @@ NGCPUserPrefs = {
 NGCPUserPrefs_MT = { __index = NGCPUserPrefs }
 
 NGCPUserPrefs_MT.__tostring = function ()
-        local output = ''
         local xavp = NGCPXAvp:new('caller','usr_prefs')
-        output = string.format("caller_usr_prefs:%s\n", tostring(xavp))
+        local output = string.format("caller_usr_prefs:%s\n", tostring(xavp))
         xavp = NGCPXAvp:new('callee','usr_prefs')
         output = output .. string.format("callee_usr_prefs:%s\n", tostring(xavp))
         return output
@@ -62,10 +61,9 @@ NGCPUserPrefs_MT.__tostring = function ()
     function NGCPUserPrefs:_defaults(level)
         local defaults = self.config:get_defaults('usr')
         local keys = {}
-        local k,_
 
         if defaults then
-            for k,v in pairs(defaults) do
+            for k,_ in pairs(defaults) do
                 table.insert(keys, k)
             end
         end
@@ -81,7 +79,6 @@ NGCPUserPrefs_MT.__tostring = function ()
         local keys
         local result = {}
         local row = cur:fetch({}, "a")
-        local k,v
         local xavp
 
         keys, defaults = self:_defaults(level)
diff --git a/ngcp/utils.lua b/ngcp/utils.lua
index 342a7cd..c0282b6 100644
--- a/ngcp/utils.lua
+++ b/ngcp/utils.lua
@@ -19,6 +19,7 @@
 --
 -- Lua utils
 
+-- luacheck: globals math table string
 -- improving the built-in pseudorandom generator
 -- http://lua-users.org/wiki/MathLibraryTutorial
 do
@@ -41,18 +42,18 @@ end
 -- copy a table
 function table.deepcopy(object)
     local lookup_table = {}
-    local function _copy(object)
-        if type(object) ~= "table" then
-            return object
-        elseif lookup_table[object] then
-            return lookup_table[object]
+    local function _copy(obj)
+        if type(obj) ~= "table" then
+            return obj
+        elseif lookup_table[obj] then
+            return lookup_table[obj]
         end
         local new_table = {}
-        lookup_table[object] = new_table
-        for index, value in pairs(object) do
+        lookup_table[obj] = new_table
+        for index, value in pairs(obj) do
             new_table[_copy(index)] = _copy(value)
         end
-        return setmetatable(new_table, getmetatable(object))
+        return setmetatable(new_table, getmetatable(obj))
     end
     return _copy(object)
 end
@@ -76,7 +77,7 @@ function table.add(t, element)
 end
 
 function table.del(t, element)
-    local _,v,i
+    local i
     local pos = {}
 
     if t then
@@ -107,8 +108,7 @@ end
 function table.size(t)
   if t then
     local c = 0
-    local _,v
-    for _,v in pairs(t) do
+    for _ in pairs(t) do
       c = c + 1
     end
     return c
@@ -162,6 +162,7 @@ function table.shuffle(tab)
   return res
 end
 
+-- luacheck: ignore range
 -- range(start)             returns an iterator from 1 to a (step = 1)
 -- range(start, stop)       returns an iterator from a to b (step = 1)
 -- range(start, stop, step) returns an iterator from a to b, counting by step.
@@ -185,17 +186,16 @@ range = function (i, to, inc)
 end
 
 function table.shift(t, position)
-  local k, v
   local res = {}
   local p = position % #t
 
   if p == 0 then return end
   for k in range(1, p) do
-    v = table.remove(t, k-#res)
+    local v = table.remove(t, k-#res)
     table.insert(res, v)
   end
-  for _,v in ipairs(res) do
-    table.insert(t, v)
+  for _,_v in ipairs(res) do
+    table.insert(t, _v)
   end
 end
 
@@ -205,6 +205,7 @@ end
 -- "'a','b'"
 -- implode("#",t)
 -- "a#b"
+-- luacheck: ignore implode explode
 function implode(delimiter, list, quoter)
     local len = #list
     if not delimiter then
@@ -265,6 +266,7 @@ end
 -- Lua 5.1 compatible
 
 -- GLOBAL
+-- luacheck: ignore Stack.*
 Stack = {
   __class__ = 'Stack'
 }
@@ -308,14 +310,15 @@ Stack_MT = {
   end
 
   -- pop a value from the stack
-  function Stack:pop(num)
+  function Stack:pop(n)
     -- get num values from stack
-    local num = num or 1
+    local num = n or 1
 
     -- return table
     local entries = {}
 
     -- get values into entries
+    -- luacheck: ignore i
     for i = 1, num do
       -- get last entry
       if #self._et ~= 0 then
diff --git a/ngcp/xavp.lua b/ngcp/xavp.lua
index 3578cb0..96aafc5 100644
--- a/ngcp/xavp.lua
+++ b/ngcp/xavp.lua
@@ -28,27 +28,26 @@ NGCPXAvp_MT = {
 }
     function NGCPXAvp:new(level,group,l)
         local t = NGCPXAvp.init(level,group,l)
-        NGCPXAvp_MT.__call = function(t, key, value)
+        NGCPXAvp_MT.__call = function(s, key, value)
             if not key then
                 error("key is empty")
             end
-            local id = string.format("$xavp(%s[0]=>%s)", t.name, key)
+            local id = string.format("$xavp(%s[0]=>%s)", s.name, key)
             --print(string.format("id:%s", id))
             if not value then
                 return sr.pv.get(id)
             elseif type(value) == "number" then
-                table.add(t.keys, key)
+                table.add(s.keys, key)
                 --sr.log("dbg", string.format("seti: [%s]:%d", id, value))
                 sr.pv.seti(id, value)
             elseif type(value) == "string" then
-                table.add(t.keys, key)
+                table.add(s.keys, key)
                 --sr.log("dbg", string.format("sets: [%s]:%s", id, value))
                 sr.pv.sets(id, value)
             elseif type(value) == "table" then
-                table.add(t.keys, key)
-                local i, v
+                table.add(s.keys, key)
                 for i = #value, 1, -1 do
-                    v = value[i]
+                    local v = value[i]
                     if type(v) == "number" then
                         sr.pv.seti(id, v)
                     elseif type(v) == "string" then
@@ -61,13 +60,12 @@ NGCPXAvp_MT = {
                 error("value is not a number or string")
             end
         end
-        NGCPXAvp_MT.__tostring = function (t)
-            local l,k,v
+        NGCPXAvp_MT.__tostring = function (s)
             local output
 
-            l = sr.xavp.get(t.name, 0)
-            if l then
-                output = table.tostring(l)
+            local ll = sr.xavp.get(s.name, 0)
+            if ll then
+                output = table.tostring(ll)
             end
             sr.log("dbg", string.format("output:%s", output))
             return output
@@ -95,7 +93,7 @@ NGCPXAvp_MT = {
     end
 
     function NGCPXAvp._setvalue(id, vtype, value)
-        local check = nil
+        local check
     	-- sr.log("info", string.format("vtype:[%s]:%d", type(vtype), vtype))
     	if type(vtype) == "string" then
     		vtype = tonumber(vtype)
@@ -119,7 +117,7 @@ NGCPXAvp_MT = {
             check = sr.pv.get(id)
             if check then
                 if type(check) == 'table' then
-                    check = table.tostring(check)
+                    table.tostring(check)
                 end
 	        else
                 --error(string.format("%s:nil", id))
@@ -129,7 +127,6 @@ NGCPXAvp_MT = {
     end
 
     function NGCPXAvp:_create(l)
-        local i
         local name = string.format("$xavp(%s=>dummy)", self.name)
         if not sr.pv.get(name) then
             NGCPXAvp._setvalue(name, 0, self.level)