diff --git a/install.sh b/install.sh
index 352bdac..b04cfba 100755
--- a/install.sh
+++ b/install.sh
@@ -55,13 +55,10 @@ function install_host() {
                 echo "$i" already overriden
             fi
         done
-        source /etc/bash.bashrc
-
-        # shellcheck disable=SC1091
-        source "$CURDIR/lib/functions.sh"
-        idem_apt_install "${REQUIRED_PKGS[@]}"
 
+        sudo /opt/debian_bash/tools/idem_apt_install "${REQUIRED_PKGS[@]}"
     fi
+
 }
 
 function install_containers() {
diff --git a/lib/functions.sh b/lib/functions.sh
index 1ef493c..c27c9fb 100644
--- a/lib/functions.sh
+++ b/lib/functions.sh
@@ -1,18 +1,5 @@
 #!/bin/bash
 
-# idempotent apt install [package1 package2 ...]
-function idem_apt_install() {
-  [ -z "${VERBOSE:-}" ] && VERBOSE=false
-  #  || echo "VERBOSE is set to $VERBOSE"
-  for i in "$@"; do
-    if ! dpkg -l "$i" 2>/dev/null | grep -q ^ii; then
-      sudo apt install -y "$i"
-    elif $VERBOSE; then
-      echo "apt package <$i> already installed!"
-    fi
-  done
-}
-
 ##
 # return 0 (true) if array (passed by name) contains element
 # usage:
diff --git a/tools/idem_apt_install b/tools/idem_apt_install
new file mode 100755
index 0000000..827c976
--- /dev/null
+++ b/tools/idem_apt_install
@@ -0,0 +1,25 @@
+#!/bin/bash
+
+function usage() {
+    local BASECMD
+    BASECMD=$(basename "$0")
+    echo "usage: $BASECMD <packages...>"
+    echo 'idempotent debian package installation : update if necessary, install only if not yet done'
+    exit 1
+}
+
+[ "$(id -u)" -ne 0 ] && echo 'root privilege required' && exit 2
+[[ $# -lt 1 ]] && usage
+
+if [ "$(date --date='-12 hours' +%s)" -gt "$(date -d "$(stat -c %y /var/lib/apt/lists/partial)" +%s)" ]; then
+    echo "updating repositoring..."
+    apt update
+fi
+
+for i in "$@"; do
+    if ! dpkg -l "$i" 2>/dev/null | grep -q ^ii; then
+        sudo apt install -y "$i"
+    elif [ -n "${VERBOSE+x}" ] && $VERBOSE; then
+        echo "apt package <$i> already installed!"
+    fi
+done