diff --git a/install.sh b/install.sh
index 8122a01..83f56ca 100755
--- a/install.sh
+++ b/install.sh
@@ -1,50 +1,43 @@
 #!/bin/bash
 
-
 BASEDIR=$PWD
-TAG=$(cat /opt/debian-bash/.semver_git_tag)
+REQUIRED_PKGS=(jq rsync file git)
 
-function usage {
-	echo 'usage: --host | --containers | --full | --one-container <CT_NAME>'
-	exit -1
+function usage() {
+    echo 'usage: --host | --containers | --full | --one-container <CT_NAME>'
+    exit -1
 }
 
-function install_host {
+function install_host() {
     echo "install on: $HOSTNAME"
     echo ----------------------
 
-    [ `id -u` -ne 0 ] && echo 'root privilege required' && exit 1
-
-	# required packages jq
-	/usr/bin/dpkg-query --status jq >/dev/null 2>&1
-	[ $? -ne 0 ] && /usr/bin/apt install -y jq
-
-	# required packages rsync
-	/usr/bin/dpkg-query --status rsync >/dev/null 2>&1
-	[ $? -ne 0 ] && /usr/bin/apt install -y rsync
+    [ $(id -u) -ne 0 ] && echo 'root privilege required' && exit 1
 
+    # shellcheck disable=SC1091
+    source "$BASEDIR/lib/functions.sh"
+    idem_apt_install "${REQUIRED_PKGS[@]}"
 
     if [[ ! $BASEDIR == '/opt/debian-bash' ]]; then
         # download and filfull /opt/debian-bash, then run it from folder
 
-		if [[ -L /opt/debian-bash ]];then
-			cd /opt/debian-bash
-			./install.sh $PARAM1
-			exit 0
-		else
-
-	        rm -rf /opt/debian-bash
-	        TEMP=`mktemp -d`
-	        cd $TEMP
-	        echo $TEMP
-	        wget https://git.artcode.re/pvincent/debian-bash/archive/master.tar.gz
-	        tar -xzf master.tar.gz
-	        mv debian-bash /opt/
-	        cd /opt/debian-bash
-	        ./install.sh $PARAM1
-	        rm -rf $TEMP
-	        exit 0
-		fi
+        if [[ -L /opt/debian-bash ]]; then
+            cd /opt/debian-bash && ./install.sh "$PARAM1"
+            exit 0
+        else
+
+            rm -rf /opt/debian-bash
+            TEMP=$(mktemp -d)
+            cd $TEMP
+            echo $TEMP
+            wget https://git.artcode.re/pvincent/debian-bash/archive/master.tar.gz
+            tar -xzf master.tar.gz
+            mv debian-bash /opt/
+            cd /opt/debian-bash
+            ./install.sh $PARAM1
+            rm -rf $TEMP
+            exit 0
+        fi
 
     else
 
@@ -56,8 +49,7 @@ function install_host {
         ORIGINAL="ORIGINAL"
         declare -a arr=(/etc/bash.bashrc /etc/inputrc /etc/vim/vimrc)
 
-        for i in "${arr[@]}"
-        do
+        for i in "${arr[@]}"; do
             if [ ! -f "$i.$ORIGINAL" ]; then
 
                 echo "$i needs installation $(basename $i)"
@@ -71,13 +63,13 @@ function install_host {
     fi
 }
 
-function install_containers {
+function install_containers() {
     echo "install containers"
     echo --------------------
 
     # install inside active LXC containers
     if [[ -f '/snap/bin/lxc' ]]; then
-        for container in `/snap/bin/lxc list --format=json | /bin/jq -r '.[] | select(.state.status == "Running") | .name'`; do
+        for container in $(/snap/bin/lxc list --format=json | /bin/jq -r '.[] | select(.state.status == "Running") | .name'); do
             install_one_container $container
             echo
         done
@@ -85,7 +77,7 @@ function install_containers {
 
 }
 
-function install_one_container {
+function install_one_container() {
     CT=$1
     echo "install container <$CT>"
     echo -------------------------
@@ -100,27 +92,25 @@ function install_one_container {
 PARAM1=$1
 
 case $PARAM1 in
-    "--host")
-        install_host
-        ;;
-    "--containers")
-        install_containers
-        ;;
-    "--one-container")
-        CT=$2
-        if [ ! -z $CT ]; then
-            install_one_container $CT
-        else
-            usage
-        fi
-        ;;
-    "--full")
-        install_host
-        install_containers
-        ;;
-    *)
+"--host")
+    install_host
+    ;;
+"--containers")
+    install_containers
+    ;;
+"--one-container")
+    CT=$2
+    if [ ! -z $CT ]; then
+        install_one_container $CT
+    else
         usage
-        ;;
+    fi
+    ;;
+"--full")
+    install_host
+    install_containers
+    ;;
+*)
+    usage
+    ;;
 esac
-
-
diff --git a/lib/functions.sh b/lib/functions.sh
index e3c3dd3..af7abe4 100644
--- a/lib/functions.sh
+++ b/lib/functions.sh
@@ -1,45 +1,53 @@
+# idempotent apt install [package1 package2 ...]
+function idem_apt_install() {
+  for i in $@; do
+    if ! (/usr/bin/dpkg-query --status "$i" >/dev/null 2>&1); then
+      /usr/bin/apt install -y "$i"
+    fi
+  done
+}
 
 ##
-# return 0 (true) if array (passed by name) contains element 
-# usage: 
+# return 0 (true) if array (passed by name) contains element
+# usage:
 #   ARRAY = ( a b c )
 #   containsElement ARRAY 'a' => 0
-containsElement () {
-	local -a 'arraykeys=("${!'"$1"'[@]}")'
+containsElement() {
+  local -a 'arraykeys=("${!'"$1"'[@]}")'
   if $(isArray $1); then
-	  for index in ${arraykeys[*]}; do 
-  		current=$1"[$index]"
-		  [[ "${!current}" == "$2" ]] && return 0; # found
-	  done
-	  return 1; # not found
+    for index in ${arraykeys[*]}; do
+      current=$1"[$index]"
+      [[ "${!current}" == "$2" ]] && return 0 # found
+    done
+    return 1 # not found
   else
-    >&2 echo "ERROR: $1 not an array!" 
-    return 2; # not an array
+    echo >&2 "ERROR: $1 not an array!"
+    return 2 # not an array
   fi
 }
 
-isArray(){
-  [[ "$(declare -p $1 2> /dev/null)" =~ "declare -a" ]] && return 0; # is an array
-  return 1; # not an array
+isArray() {
+  [[ "$(declare -p $1 2>/dev/null)" =~ "declare -a" ]] && return 0 # is an array
+  return 1                                                         # not an array
 }
 
 ##
-# 
-askConfirmation () {
+#
+askConfirmation() {
   case "$1" in
-    y|Y|yes|YES ) 
-      QUESTION="(Y/n)?"
-      DEFAULT=0
-      ;;
-    * ) 
-      QUESTION="(y/N)?"
-      DEFAULT=1
-      ;;
+  y | Y | yes | YES)
+    QUESTION="(Y/n)?"
+    DEFAULT=0
+    ;;
+  *)
+    QUESTION="(y/N)?"
+    DEFAULT=1
+    ;;
   esac
   read -p "$QUESTION : " choice
-  case "$choice" in 
-    y|Y|yes|YES ) return 0;; #true
-    n|no|N|NO ) return 1;; #false
-    * ) return $DEFAULT;;
-  esac  
-}
\ No newline at end of file
+  case "$choice" in
+  y | Y | yes | YES) return 0 ;; #true
+  n | no | N | NO) return 1 ;;   #false
+  *) return $DEFAULT ;;
+  esac
+}