diff --git a/functions b/functions
index adcf5bdaa1..c4d56a236f 100644
--- a/functions
+++ b/functions
@@ -4,7 +4,7 @@
 # apt-get wrapper to set arguments correctly
 # apt_get package [package ...]
 function apt_get() {
-    [[ "$OFFLINE" = "True" ]] && return
+    [[ "$OFFLINE" = "True" || -z "$@" ]] && return
     local sudo="sudo"
     [[ "$(id -u)" = "0" ]] && sudo="env"
     $sudo DEBIAN_FRONTEND=noninteractive \
@@ -124,7 +124,7 @@ function is_set() {
 # pip install wrapper to set cache and proxy environment variables
 # pip_install package [package ...]
 function pip_install {
-    [[ "$OFFLINE" = "True" ]] && return
+    [[ "$OFFLINE" = "True" || -z "$@" ]] && return
     sudo PIP_DOWNLOAD_CACHE=/var/cache/pip \
         HTTP_PROXY=$http_proxy \
         HTTPS_PROXY=$https_proxy \
diff --git a/stack.sh b/stack.sh
index 9fd95c12c5..cefd635994 100755
--- a/stack.sh
+++ b/stack.sh
@@ -538,12 +538,16 @@ fi
 #    dist:DISTRO1,DISTRO2 it will be installed only for those
 #    distros (case insensitive).
 function get_packages() {
-    local file_to_parse="general"
+    local package_dir=$1
+    local file_to_parse
     local service
 
-    for service in ${ENABLED_SERVICES//,/ }; do
-        # Allow individual services to specify dependencies
-        if [[ -e $FILES/apts/${service} ]]; then
+    if [[ -z "$package_dir" ]]; then
+        echo "No package directory supplied"
+        return 1
+    fi
+    for service in general ${ENABLED_SERVICES//,/ }; do        # Allow individual services to specify dependencies
+        if [[ -e ${package_dir}/${service} ]]; then
             file_to_parse="${file_to_parse} $service"
         fi
         if [[ $service == n-* ]]; then
@@ -562,9 +566,9 @@ function get_packages() {
     done
 
     for file in ${file_to_parse}; do
-        local fname=${FILES}/apts/${file}
+        local fname=${package_dir}/${file}
         local OIFS line package distros distro
-        [[ -e $fname ]] || { echo "missing: $fname"; exit 1 ;}
+        [[ -e $fname ]] || continue
 
         OIFS=$IFS
         IFS=$'\n'
@@ -590,10 +594,10 @@ function get_packages() {
 
 # install apt requirements
 apt_get update
-apt_get install $(get_packages)
+apt_get install $(get_packages $FILES/apts)
 
 # install python requirements
-pip_install `cat $FILES/pips/* | uniq`
+pip_install $(get_packages $FILES/pips | sort -u)
 
 # compute service
 git_clone $NOVA_REPO $NOVA_DIR $NOVA_BRANCH