diff --git a/action.yml b/action.yml
index d71c7ec..2ad3a98 100644
--- a/action.yml
+++ b/action.yml
@@ -22,5 +22,5 @@ runs:
         key: cache-apt-pkgs_${{ inputs.cache_key }}
 
     - name: Install Packages
-      run: ${{ github.action_path }}/run.sh "~/cache-apt-pkgs" "${{ inputs.packages }}"
+      run: ${{ github.action_path }}/run.sh / ~/cache-apt-pkgs ${{ inputs.packages }}
       shell: bash
diff --git a/run.sh b/run.sh
index 4c0af79..a2e6061 100755
--- a/run.sh
+++ b/run.sh
@@ -1,84 +1,147 @@
-#!/bin/bash -x
+#!/bin/bash
 
+# Directory that holds the cached packages.
 cache_dir=$1
-packages="${@:2}"
+# Root directory to untar the cached packages to.
+# Typically filesystem root '/' but can be changed for testing.
+cache_restore_root=$2
+# List of the packages to use.
+packages="${@:3}"
 
+##############################################################################
+# Validate command line arguments.
+# Globals:
+#   cache_dir
+# Arguments:
+#   None
+# Outputs:
+#   None
+# Side effects:
+#   Exits if validation fails.
+##############################################################################
 validate_args() {
-  echo -n "Validating action arguments... ";
+  echo -n "* Validating action arguments... ";
   if [ ! -d "$cache_dir" ]; then
-    echo "aborted.\nCache directory '$cache_dir' does not exist."
-    return 1
+    echo "aborted."
+    echo "Cache directory '$cache_dir' does not exist." >&2
+    exit 1
   fi
-  if [ $packages = "" ]; then
-    echo "aborted.\nPackages argument cannot be empty."
-    return 2
+  if [ "$packages" == "" ]; then
+    echo "aborted."
+    echo "* Packages argument cannot be empty." >&2
+    exit 2
   fi
   for package in $packages; do
-    if apt-cache search ^$package$ | grep $package; then
-      echo "aborted.\nPackage '$package' not found."
-      return 3
+    apt-cache search ^$package$ | grep $package > /dev/null
+    if [ $? -ne 0 ]; then
+      echo "aborted."
+      echo "* Package '$package' not found." >&2
+      exit 3
     fi
   done
   echo "done."
-  return 0
 }
 
+##############################################################################
+# Get cached package file path.
+# Globals:
+#   cache_dir
+# Arguments:
+#   package name
+# Outputs:
+#   Writes cached package file path to stdout.
+##############################################################################
+get_cache_filepath() {  
+  echo "$cache_dir/$1.tar.gz"
+}
+
+##############################################################################
+# Clean the cache directory of unused packages.
+# Globals:
+#   cache_dir
+# Arguments:
+#   None
+# Outputs:
+#   None
+# Side effects:
+#   Removes unused cached packages from filesystem.
+##############################################################################
 clean_cache() {
-  for dir in `ls $cache_dir`; do
+  for listed_filepath in $(find $cache_dir -maxdepth 1 -type f); do
     remove=true
     for package in $packages; do
-      if [ $dir == $package ]; then
+      cache_filepath=$(get_cache_filepath $package)
+      if [ $listed_filepath == $cache_filepath ]; then
         remove=false
         break
       fi
-    done
-    [ $remove ] && rm -fr $cache_dir/$dir
+    done    
+    if [ $remove == true ]; then
+      rm -f $listed_filepath
+      echo "* Removed unused cached file $listed_filepath."
+    fi
   done
 }
 
+##############################################################################
+# Restore cached package.
+# Globals:
+#   cache_restore_root
+# Arguments:
+#   package
+# Outputs:
+#   None
+# Side effects;
+#   Untars files to filesystem and performs an APT upgrade.
+##############################################################################
 restore_pkg() {
   package=$1
-  package_dir=$2
+  cache_filepath=$(get_cache_filepath $package)
 
-  echo -n "Restoring $package from cache $package_dir... "
-  sudo cp --verbose --force --recursive $package_dir/* /
+  echo "* Restoring $package from cache $cache_filepath... "
+  tar -xf $cache_filepath -C $cache_restore_root
   sudo apt-get --yes --only-upgrade install $package
-  echo "done."
 }
 
+##############################################################################
+# Install package and cache it to the filesystem.
+# Globals:
+#   None
+# Arguments:
+#   package
+# Outputs:
+#   None
+# Side effects;
+#   Performs an APT install of the package and creates the cached package.
+##############################################################################
 install_and_cache_pkg() {
   package=$1
-  package_dir=$2
+  cache_filepath=$(get_cache_filepath $package)
 
-  echo -n "Clean installing $package... "
-  sudo apt-get --yes install $package
-  echo "done."
+  echo "* Clean installing $package... "
+  sudo apt-get --yes install $package  
 
-  echo -n "Caching $package to $package_dir..."
-  mkdir --parents $package_dir
-  # Pipe all package files (no folders) to copy command.
-  sudo dpkg -L $package | 
+  echo "* Caching $package to $cache_filepath..."
+  # Pipe all package files (no folders) to Tar.
+  dpkg -L $package |
     while IFS= read -r f; do 
       if test -f $f; then echo $f; fi;
     done | 
-    xargs cp -p -t $package_dir
-  echo "done."
+    xargs tar -czf $cache_filepath -C /
 }
 
-validate_code = validate_args
-if validate_code -ne 0; then
-  exit $validate_code
-fi
-
+validate_args
 clean_cache
 
 for package in $packages; do
-  package_dir=$cache_dir/$package
-  if [ -d $package_dir ]; then
-    restore_pkg $package $package_dir
+  echo "* Processing package $package..."
+  cache_filepath=$(get_cache_filepath $package)
+  echo $cache_filepath
+  if [ -f $cache_filepath ]; then
+    restore_pkg $package
   else
-    install_and_cache_pkg $package $package_dir
+    install_and_cache_pkg $package
   fi
 done
 
-echo "Action complete. ${#packages[@]} packages installed."
+echo "Action complete. ${#packages[@]} package(s) installed."