diff --git a/setup.sh b/setup.sh
index e69de29b..65895729 100644
--- a/setup.sh
+++ b/setup.sh
@@ -0,0 +1,82 @@
+#!/bin/bash
+#########################################################
+# This script is intended to be run like this:
+#
+#   curl https://mailinabox.email/setup.sh | sudo bash
+#
+#########################################################
+
+if [ -z "$TAG" ]; then
+	# If a version to install isn't explicitly given as an environment
+	# variable, then install the latest version. But the latest version
+	# depends on the operating system. Existing Ubuntu 14.04 users need
+	# to be able to upgrade to the latest version supporting Ubuntu 14.04,
+	# in part because an upgrade is required before jumping to Ubuntu 18.04.
+	# New users on Ubuntu 18.04 need to get the latest version number too.
+	#
+	# Also, the system status checks read this script for TAG = (without the
+	# space, but if we put it in a comment it would confuse the status checks!)
+	# to get the latest version, so the first such line must be the one that we
+	# want to display in status checks.
+	if [ "$(lsb_release -d | sed 's/.*:\s*//' | sed 's/18\.04\.[0-9]/18.04/' )" == "Ubuntu 18.04 LTS" ]; then
+		# This machine is running Ubuntu 18.04.
+		TAG=v56
+
+	elif [ "$(lsb_release -d | sed 's/.*:\s*//' | sed 's/14\.04\.[0-9]/14.04/' )" == "Ubuntu 14.04 LTS" ]; then
+		# This machine is running Ubuntu 14.04.
+		echo "You are installing the last version of Mail-in-a-Box that will"
+		echo "support Ubuntu 14.04. If this is a new installation of Mail-in-a-Box,"
+		echo "stop now and switch to a machine running Ubuntu 18.04. If you are"
+		echo "upgrading an existing Mail-in-a-Box --- great. After upgrading this"
+		echo "box, please visit https://mailinabox.email for notes on how to upgrade"
+		echo "to Ubuntu 18.04."
+		echo ""
+		TAG=v0.30
+
+	else
+		echo "This script must be run on a system running Ubuntu 18.04 or Ubuntu 14.04."
+		exit 1
+	fi
+fi
+
+# Are we running as root?
+if [[ $EUID -ne 0 ]]; then
+	echo "This script must be run as root. Did you leave out sudo?"
+	exit 1
+fi
+
+# Clone the Mail-in-a-Box repository if it doesn't exist.
+if [ ! -d $HOME/mailinabox ]; then
+	if [ ! -f /usr/bin/git ]; then
+		echo Installing git . . .
+		apt-get -q -q update
+		DEBIAN_FRONTEND=noninteractive apt-get -q -q install -y git < /dev/null
+		echo
+	fi
+
+	echo Downloading Mail-in-a-Box $TAG. . .
+	git clone \
+		-b $TAG --depth 1 \
+		https://github.com/mail-in-a-box/mailinabox \
+		$HOME/mailinabox \
+		< /dev/null 2> /dev/null
+
+	echo
+fi
+
+# Change directory to it.
+cd $HOME/mailinabox
+
+# Update it.
+if [ "$TAG" != $(git describe) ]; then
+	echo Updating Mail-in-a-Box to $TAG . . .
+	git fetch --depth 1 --force --prune origin tag $TAG
+	if ! git checkout -q $TAG; then
+		echo "Update failed. Did you modify something in $(pwd)?"
+		exit 1
+	fi
+	echo
+fi
+
+# Start setup script.
+setup/start.sh
\ No newline at end of file