diff --git a/image/cleanup.sh b/image/cleanup.sh
index bf718ad..2e358d5 100755
--- a/image/cleanup.sh
+++ b/image/cleanup.sh
@@ -6,5 +6,7 @@ set -x
 apt-get clean
 rm -rf /build
 rm -rf /tmp/* /var/tmp/*
+rm -rf /var/lib/apt/lists/*
+rm -f /etc/dpkg/dpkg.cfg.d/02apt-speedup
 
 rm -f /etc/ssh/ssh_host_*
diff --git a/image/prepare.sh b/image/prepare.sh
index a44937b..b30df58 100755
--- a/image/prepare.sh
+++ b/image/prepare.sh
@@ -3,6 +3,9 @@ set -e
 source /build/buildconfig
 set -x
 
+## Temporarily disable dpkg fsync to make building faster.
+echo force-unsafe-io > /etc/dpkg/dpkg.cfg.d/02apt-speedup
+
 ## Enable Ubuntu Universe.
 echo deb http://archive.ubuntu.com/ubuntu precise main universe > /etc/apt/sources.list
 echo deb http://archive.ubuntu.com/ubuntu precise-updates main universe >> /etc/apt/sources.list