add taoswrapper and install hook. now it works.

snap/hooks/install

+#!/bin/sh
+
+if [ ! -d /var/lib/taos ]; then
+  mkdir -p /var/lib/taos
+fi
+
+if [ ! -d /var/log/taos ]; then
+  mkdir -p -m777 /var/log/taos
+fi
+
+if [ ! -d /etc/taos ]; then
+  mkdir -p /etc/taos
+fi
+
+if [ ! -f /etc/taos/taos.cfg ]; then
+  cp $SNAP/etc/taos/taos.cfg /etc/taos/taos.cfg
+fi

snap/local/launcher.sh

@@ -15,7 +15,11 @@ case "$SNAP_USER_COMMON" in
 	*)                             COMMON=$SNAP_USER_COMMON ;;
 esac
 
-CONFIG_FILE="$SNAP/etc/taos"
+if [ -d /etc/taos ]; then
+    CONFIG_FILE="/etc/taos"
+else
+    CONFIG_FILE="$SNAP/etc/taos"
+fi
 
 # Launch the snap
 $SNAP/usr/bin/taosd -c $CONFIG_FILE $@

snap/local/taoswrapper.sh

+#!/bin/sh
+# Wrapper to check for custom config in $SNAP_USER_COMMON or $SNAP_COMMON and
+# use it otherwise fall back to the included basic config which will at least
+# allow mosquitto to run and do something.
+# This script will also copy the full example config in to SNAP_USER_COMMON or
+# SNAP_COMMON so that people can refer to it.
+#
+# The decision about whether to use SNAP_USER_COMMON or SNAP_COMMON is taken
+# based on the user that runs the command. If the user is root, it is assumed
+# that mosquitto is being run as a system daemon, and SNAP_COMMON will be used.
+# If a non-root user runs the command, then SNAP_USER_COMMON will be used.
+
+case "$SNAP_USER_COMMON" in
+	*/root/snap/tdengine/common*) COMMON=$SNAP_COMMON ;;
+	*)                             COMMON=$SNAP_USER_COMMON ;;
+esac
+
+if [ -d /etc/taos ]; then
+    CONFIG_FILE="/etc/taos"
+else
+    CONFIG_FILE="$SNAP/etc/taos"
+fi
+
+# Launch the snap
+$SNAP/usr/bin/taos -c $CONFIG_FILE $@

snap/snapcraft.yaml

 name: tdengine
 base: core18 # the base snap is the execution environment for this snap
 version: '2.0.0.6' # just for humans, typically '1.2+git' or '1.3.2'
-summary: Single-line elevator pitch for your amazing snap # 79 char long summary
+summary: an open-source big data platform designed and optimized for IoT. 
 description: |
   TDengine is an open-source big data platform designed and optimized for Internet of Things (IoT), Connected Vehicles, and Industrial IoT. Besides the 10x faster time-series database, it provides caching, stream computing, message queuing and other functionalities to reduce the complexity and costs of development and operations.
 
@@ -16,19 +16,25 @@ apps:
     plugs:
       - network
       - network-bind
+      - system-observe
       - systemfiles
 
   taos:
-    command: usr/bin/taos
+    command: taoswrapper.sh
     plugs:
       - network
       - systemfiles
 
+  taosdemo:
+    command: usr/bin/taosdemo
+    plugs:
+      - network
+
 plugs:
   systemfiles:
     interface: system-files
     read:
-      - /etc/taos
+      - /etc
       - /var/lib/taos
       - /tmp
     write:
@@ -42,6 +48,7 @@ parts:
     source: snap/local/
     prime:
       - launcher.sh
+      - taoswrapper.sh
 
   tdengine:
     source: .
@@ -57,12 +64,21 @@ parts:
       if [ ! -d $SNAPCRAFT_STAGE/usr ]; then
         mkdir $SNAPCRAFT_STAGE/usr
       fi
+
       if [ ! -d $SNAPCRAFT_STAGE/etc/taos ]; then
         mkdir -p $SNAPCRAFT_STAGE/etc/taos
       fi
+
       cp $SNAPCRAFT_PART_BUILD/build/* -rf $SNAPCRAFT_STAGE/usr/
       cp $SNAPCRAFT_PART_SRC/packaging/cfg/taos.cfg -rf $SNAPCRAFT_STAGE/etc/taos/
 
+      if [ ! -d $SNAPCRAFT_STAGE/var/lib/taos ]; then
+        mkdir -p $SNAPCRAFT_STAGE/var/lib/taos
+      fi
+      if [ ! -d $SNAPCRAFT_STAGE/var/log/taos ]; then
+        mkdir -p $SNAPCRAFT_STAGE/var/log/taos
+      fi
+
     prime:
       - etc/taos/taos.cfg
       - usr/bin/taosd
@@ -72,7 +88,24 @@ parts:
       - usr/lib/libtaos.so.1
       - usr/lib/libtaos.so
 
+    override-prime: |
+      snapcraftctl prime
+      if [ ! -d $SNAPCRAFT_STAGE/var/lib/taos ]; then
+        cp -rf $SNAPCRAFT_STAGE/var/lib/taos $SNAPCRAFT_PRIME
+      fi
+      if [ ! -d $SNAPCRAFT_STAGE/var/log/taos ]; then
+        cp -rf  $SNAPCRAFT_STAGE/var/log/taos $SNAPCRAFT_PRIME
+      fi
+
+layout:
+  /var/lib/taos:
+    bind: $SNAP_DATA/var/lib/taos
+  /var/log/taos:
+    bind: $SNAP_DATA/var/log/taos
+  /etc/taos/taos.cfg:
+    bind-file: $SNAP_DATA/etc/taos/taos.cfg
+
 
-    #layout:
-    #  usr/bin/taosd:
-    #bind-file: debug/build/bin/taosd
+hooks:
+  install:
+    plugs: [systemfiles]