Add pruning images except given tag

README.md

@@ -216,6 +216,15 @@ docker::image { 'ubuntu':
 
 Note: images will only install if an image of that name does not already exist.
 
+You can also remove all the images versions except the single tag you need. This is useful for keeping the disk space usage low.   
+
+```puppet
+docker::image { 'ubuntu':
+  image_tag   => 'precise',
+  image_prune => true,
+}
+```
+
 A images can also be added/build from a dockerfile with the `docker_file` property, this equivalent to running `docker build -t ubuntu - < /tmp/Dockerfile`
 
 ```puppet
@@ -236,7 +245,7 @@ You can trigger a rebuild of the image by subscribing to external events like Do
 
 ```puppet
 docker::image { 'ubuntu':
-  docker_file => '/tmp/Dockerfile'
+  docker_file => '/tmp/Dockerfile',
   subscribe => File['/tmp/Dockerfile'],
 }
 

manifests/image.pp

@@ -17,6 +17,9 @@
 # [*image_digest*]
 #   If you want a specific content digest of the image to be installed
 #
+# [*image_prune*]
+#   If you want to remove all the images except the specified tag
+#
 # [*docker_file*]
 #   If you want to add a docker image from specific docker file
 #
@@ -28,6 +31,7 @@
   $image        = $title,
   $image_tag    = undef,
   $image_digest = undef,
+  $image_prune  = false,
   $force        = false,
   $docker_file  = undef,
   $docker_dir   = undef,
@@ -37,6 +41,7 @@
   $docker_command = $docker::params::docker_command
   validate_re($ensure, '^(present|absent|latest)$')
   validate_re($image, '^[\S]*$')
+  validate_bool($image_prune)
   validate_bool($force)
 
   # Wrapper used to ensure images are up to date
@@ -50,6 +55,10 @@
     }
   )
 
+  if ($image_prune) and (!$image_tag) {
+    fail 'docker::image $image_prune requires $image_tag to be set'
+  }
+
   if ($docker_file) and ($docker_dir) {
     fail 'docker::image must not have both $docker_file and $docker_dir set'
   }
@@ -129,4 +138,17 @@
     }
   }
 
+  if $image_tag {
+    # get images with same image name, but other tags than given
+    $images_to_prune = "${docker_command} images | egrep '^(docker.io/)?${image} ' | grep -v -P '${image}\\s+${image_tag}' | awk '{ print \$3 }'"
+
+    $images_prune = "${docker_command} rmi -f $($images_to_prune)"
+
+    exec { $images_prune:
+      environment => 'HOME=/root',
+      path        => ['/bin', '/usr/bin'],
+      timeout     => 0,
+      onlyif      => "$images_to_prune | grep -P '.'",
+    }
+  }
 }

spec/defines/image_spec.rb

@@ -168,4 +168,19 @@
       }.to raise_error(Puppet::Error)
     end
   end
+
+  context 'with image_prune => true' do
+    let(:params) { { 'image_prune' => true } }
+    it do
+      expect {
+        should have_exec_resource_count(1)
+      }.to raise_error(Puppet::Error)
+    end
+  end
+
+  context 'with image_prune => true and image_tag => precise' do
+    let(:params) { { 'image_prune' => true , 'image_tag' => 'precise'} }
+    it { should contain_exec('docker rmi -f $(docker images | egrep '^(docker.io/)?base ' | grep -v -P 'base\s+precise' | awk '{ print \$3 }')') }
+  end
+
 end