Fix working directory problems with custom NB_USER

Improve start.sh logging along the way

base-notebook/start.sh

@@ -6,18 +6,23 @@ set -e
 
 # Handle special flags if we're root
 if [ $(id -u) == 0 ] ; then
+    # Switch to the root of the container in case we start adjusting paths
+    # that impact the default working directory
+    cd /
+
     # Handle username change. Since this is cheap, do this unconditionally
-    usermod -d /home/$NB_USER -l $NB_USER jovyan
+    echo "Set username to: $NB_USER"
+    usermod -m -d /home/$NB_USER -l $NB_USER jovyan
 
     # Change UID of NB_USER to NB_UID if it does not match
     if [ "$NB_UID" != $(id -u $NB_USER) ] ; then
-        echo "Set user UID to: $NB_UID"
+        echo "Set $NB_USER UID to: $NB_UID"
         usermod -u $NB_UID $NB_USER
     fi
 
     # Change GID of NB_USER to NB_GID if NB_GID is passed as a parameter
     if [ "$NB_GID" ] ; then
-        echo "Change GID to $NB_GID"
+        echo "Set $NB_USER GID to: $NB_GID"
         groupmod -g $NB_GID -o $(id -g -n $NB_USER)
     fi
 
@@ -27,8 +32,11 @@ if [ $(id -u) == 0 ] ; then
         echo "$NB_USER ALL=(ALL) NOPASSWD:ALL" > /etc/sudoers.d/notebook
     fi
 
+    # Switch to the user's home directory after adjusting any paths
+    cd /home/$NB_USER
+
     # Exec the command as NB_USER
-    echo "Execute the command as $NB_USER"
+    echo "Execute the command: $*"
     exec su $NB_USER -c "env PATH=$PATH $*"
 else
   if [[ ! -z "$NB_UID" && "$NB_UID" != "$(id -u)" ]]; then
@@ -41,6 +49,6 @@ else
       echo 'Container must be run as root to grant sudo permissions'
   fi
     # Exec the command
-    echo "Execute the command"
+    echo "Execute the command: $*"
     exec $*
 fi