diff --git a/cmake/install.inc b/cmake/install.inc
index f5e01e2f1d79f1c2e7fa32552cbe93677de6338d..c7fbd6df794f4a414b7b28e31b0c73ba3a4da906 100755
--- a/cmake/install.inc
+++ b/cmake/install.inc
@@ -16,6 +16,7 @@ ELSEIF (TD_WINDOWS)
   INSTALL(DIRECTORY ${TD_COMMUNITY_DIR}/tests/examples DESTINATION .)
   INSTALL(DIRECTORY ${TD_COMMUNITY_DIR}/packaging/cfg DESTINATION .)
   INSTALL(FILES ${TD_COMMUNITY_DIR}/src/inc/taos.h DESTINATION include)
+  INSTALL(FILES ${TD_COMMUNITY_DIR}/src/inc/taoserror.h DESTINATION include)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.lib DESTINATION driver)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.exp DESTINATION driver)
   INSTALL(FILES ${LIBRARY_OUTPUT_PATH}/taos.dll DESTINATION driver) 
diff --git a/packaging/docker/Dockerfile b/packaging/docker/Dockerfile
index b4497e210ff470e4f95894ec8f61e8b968f7b80a..0f138be4d46cc4f6d9dffc1d538d374b187a2b42 100644
--- a/packaging/docker/Dockerfile
+++ b/packaging/docker/Dockerfile
@@ -1,4 +1,4 @@
-FROM centos:7
+FROM ubuntu:16
 
 WORKDIR /root
 
diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index d55be5b8c0e08bb5b0f6745b41328f07d37a7e90..b0d8d8983bab473b8711d19805cea0fef2f10ee7 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -1,6 +1,6 @@
 name: tdengine
 base: core18
-version: 'RELEASE_VERSION'
+version: '2.0.5.1'
 icon: snap/gui/t-dengine.svg
 summary: an open-source big data platform designed and optimized for IoT. 
 description: |
@@ -72,7 +72,7 @@ parts:
       - usr/bin/taosd
       - usr/bin/taos
       - usr/bin/taosdemo
-      - usr/lib/libtaos.so.RELEASE_VERSION
+      - usr/lib/libtaos.so.2.0.5.1
       - usr/lib/libtaos.so.1
       - usr/lib/libtaos.so
 
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index ef8625da06c349b14b9bc9294462bf627da5bb5b..9b62177191d13058d161003fd98bbe28bc4df7ee 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -28,6 +28,7 @@
 #include "tutil.h"
 #include "ttimer.h"
 #include "tscProfile.h"
+#include "ttimer.h"
 
 static bool validImpl(const char* str, size_t maxsize) {
   if (str == NULL) {
@@ -257,10 +258,21 @@ TAOS *taos_connect_a(char *ip, char *user, char *pass, char *db, uint16_t port,
 void taos_close(TAOS *taos) {
   STscObj *pObj = (STscObj *)taos;
 
-  if (pObj == NULL || pObj->signature != pObj)  {
+  if (pObj == NULL) {
+    tscDebug("(null) try to free tscObj and close dnodeConn");
     return;
   }
 
+  tscDebug("%p try to free tscObj and close dnodeConn:%p", pObj, pObj->pDnodeConn);
+  if (pObj->signature != pObj) {
+    tscDebug("%p already closed or invalid tscObj", pObj);
+    return;
+  }
+
+  // make sure that the close connection can only be executed once.
+  pObj->signature = NULL;
+  taosTmrStopA(&(pObj->pTimer));
+
   SSqlObj* pHb = pObj->pHb;
   if (pHb != NULL && atomic_val_compare_exchange_ptr(&pObj->pHb, pHb, 0) == pHb) {
     if (pHb->pRpcCtx != NULL) {  // wait for rsp from dnode
diff --git a/src/os/src/linux/CMakeLists.txt b/src/os/src/linux/CMakeLists.txt
index 752326cc1de74550afac386ad5ac84f6d2f48990..b1a7ebf54e58bbbdeea6d5cc219904916cc2ba03 100644
--- a/src/os/src/linux/CMakeLists.txt
+++ b/src/os/src/linux/CMakeLists.txt
@@ -4,4 +4,4 @@ PROJECT(TDengine)
 AUX_SOURCE_DIRECTORY(. SRC)
 
 ADD_LIBRARY(os ${SRC})
-TARGET_LINK_LIBRARIES(os m rt)
+TARGET_LINK_LIBRARIES(os m rt z)