From f107309c4867a6d762409ee3f47689b01fc379af Mon Sep 17 00:00:00 2001
From: Brian Candler <brian@nsrc.org>
Date: Sat, 14 May 2016 11:03:52 +0000
Subject: [PATCH] Add qcow2 extension. Disk and RAM options

---
 README.md | 24 ++++++++++++++++++++++--
 vtp.json  | 10 +++++++++-
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index aa1b32d..31ec8fa 100644
--- a/README.md
+++ b/README.md
@@ -107,7 +107,27 @@ You get more information if you run:
 PACKER_LOG=1 ./packer build foo.json
 ~~~
 
-## Ubuntu ISO installation
+## Disk usage
+
+After an initial build of just the OS, the qcow2 file was around 2GB.
+Examining the image showed that only 1.2GB was used for the root filesystem;
+there may be temporary files which were deleted, or there may be data in the
+swap space.
+
+The default install used 512MB of RAM and created 512MB of swap. This can be
+increased with e.g. `"qemuargs": [ [ "-m", "768M" ] ]`
+
+TODO: minimise the image size by running zerofree on all filesystems (this
+cannot be done while root is mounted read-write), and wiping the swap space.
+
+Normally packer runs a qemu-img convert pass to remove empty space in the image.
+This can be disabled by `"skip_compaction": true`: this speeds up the build a
+bit, but increases the qcow2 file size from 2GB to 2.8GB
+
+Adding `"disk_compression": true` reduces the size of the qcow2 image to
+about 800MB, at the cost of slowing down the build.
+
+# Ubuntu ISO installation
 
 For an [automated Ubuntu install](https://help.ubuntu.com/lts/installation-guide/amd64/ch04s06.html)
 there are two options: [preseeding](https://help.ubuntu.com/lts/installation-guide/amd64/apb.html)
@@ -132,7 +152,7 @@ and to have compression on the root.
 QCOW2 images can be loopback-mounted with a bit of help from nbd:
 
     modprobe nbd
-    qemu-nbd -c /dev/nbd0 /path/to/image.qcow2
+    qemu-nbd -c /dev/nbd0 output-qemu/vtp.qcow2
     mount /dev/nbd0p1 /mnt
     ...
     umount /mnt
diff --git a/vtp.json b/vtp.json
index c969fe2..f8214d2 100644
--- a/vtp.json
+++ b/vtp.json
@@ -1,16 +1,24 @@
 {
+  "_comment": "Based on https://github.com/puppetlabs/puppetlabs-packer/blob/master/templates/ubuntu-16.04/x86_64.vmware.base.json",
+
   "variables": {
     "headless": "false"
   },
+
   "builders":
   [
     {
       "type": "qemu",
       "format": "qcow2",
       "accelerator": "kvm",
+      "qemuargs": [
+        [ "-m", "512M" ]
+      ],
       "net_device": "virtio-net",
       "disk_interface": "virtio",
-      "vm_name": "vtp",
+      "vm_name": "vtp.qcow2",
+      "skip_compaction": false,
+      "disk_compression": false,
       "floppy_files": [ "preseed.cfg" ],
       "boot_command": [
         "<enter><wait><f6><esc><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs><bs>",
-- 
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