diff --git a/defaults/main.yml b/defaults/main.yml
index ead56f6..b8aa984 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -18,3 +18,4 @@ r_environment: {}
 r_scripts_install_path: /usr/local/bin
 r_scripts_install_owner: root
 r_scripts_install_group: root
+r_list_packages_once: false
diff --git a/tasks/get_list_packages.yml b/tasks/get_list_packages.yml
new file mode 100644
index 0000000..7bf9c78
--- /dev/null
+++ b/tasks/get_list_packages.yml
@@ -0,0 +1,16 @@
+---
+
+- name: packages | list installed packages
+  command: >
+    R-list-installed-packages {{ r_packages_lib }}
+  environment: "{{ r_environment }}"
+  register: _r_installed_packages
+  changed_when: false
+  tags:
+    - r-list-installed-packages
+
+- name: packages | set_fact list installed packages
+  set_fact:
+    r_installed_packages: "{{ _r_installed_packages.stdout_lines }}"
+  tags:
+    - r-list-installed-packages
diff --git a/tasks/packages.yml b/tasks/packages.yml
index 3231073..592703c 100644
--- a/tasks/packages.yml
+++ b/tasks/packages.yml
@@ -8,19 +8,23 @@
     group: "{{ r_scripts_install_group }}"
     mode: 0755
   with_items:
+    - src: R-list-installed-packages.j2
+      dest: R-list-installed-packages
     - src: R-install-package.j2
       dest: R-install-package
     - src: R-remove-package.j2
       dest: R-remove-package
     - src: R-update-package.j2
       dest: R-update-package
-    - src: R-update-packages.j2
-      dest: R-update-packages
     - src: R-install-requirements.j2
       dest: R-install-requirements
   tags:
     - r-packages-copy-r-scripts
 
+- name: packages | init the package lists
+  include: get_list_packages.yml
+  when: r_list_packages_once
+
 - name: packages | install
   command: >
     {{ r_scripts_install_path }}/R-install-package
@@ -37,7 +41,9 @@
         r_packages_from_bioconductor | ternary ((r_version is version('35', '>=') | ternary (r_preset_package_bioconductor, [])), []) +
         r_packages
     }}"
-  when: item.state is undefined or item.state == 'present'
+  when:
+    - not r_list_packages_once or item.name not in r_installed_packages
+    - item.state is undefined or item.state == 'present'
   tags:
     - r-packages-install
 
@@ -51,6 +57,7 @@
   changed_when: "_r_remove_package.stdout_lines[-1] is defined and _r_remove_package.stdout_lines[-1] == 'changed'"
   with_items: "{{ r_packages }}"
   when:
+    - not r_list_packages_once or item.name in r_installed_packages
     - item.state is defined
     - item.state == 'absent'
   tags:
diff --git a/templates/R-install-package.j2 b/templates/R-install-package.j2
index 970cc16..94c7dbd 100644
--- a/templates/R-install-package.j2
+++ b/templates/R-install-package.j2
@@ -16,7 +16,9 @@ if (type == 'github') {
   package = argv[1];
 }
 
+{% if r_list_packages_once == false %}
 if (!(package %in% installed.packages(lib.loc = lib)[, 'Package'])) {
+{% endif %}
   if (type == 'cran') {
     repos = ifelse(is.na(argv[4]), '{{ r_packages_repos.rstrip('/') }}', argv[4]);
 
@@ -52,4 +54,6 @@ if (!(package %in% installed.packages(lib.loc = lib)[, 'Package'])) {
     cat("Unrecognised type\n");
     q(status = 1);
   }
+{% if r_list_packages_once == false %}
 }
+{% endif %}
diff --git a/templates/R-list-installed-packages.j2 b/templates/R-list-installed-packages.j2
new file mode 100644
index 0000000..843f33d
--- /dev/null
+++ b/templates/R-list-installed-packages.j2
@@ -0,0 +1,12 @@
+#!/usr/bin/env Rscript
+
+argv = commandArgs(trailingOnly = TRUE);
+if (is.null(argv) | length(argv) < 1) {
+  cat("Usage: R-list-installed-packages [lib]\n");
+  q(status = 1);
+}
+
+lib = ifelse(is.na(argv[1]), '{{ r_packages_lib }}', argv[1]);
+
+cat(paste(installed.packages(lib.loc = lib)[, 'Package'], collapse="\n"))
+