entrypoint.sh

#!/bin/bash
ARGS=$@

echo "Docker: $(dockerd --version)"
echo "Kernel: $(/linux/linux --version)"
echo "Rootfs: $(lsb_release -ds)"
echo
echo "Configuration: MEM=$MEM DISK=$DISK"

#start sshd
/etc/init.d/ssh start

# Create the ext4 volume image for /var/lib/docker
if [ ! -f /persistent/var_lib_docker.img ]; then
    echo "Formatting /persistent/var_lib_docker.img"
    dd if=/dev/zero of=/persistent/var_lib_docker.img bs=1 count=0 seek=${DISK} > /dev/null 2>&1
    mkfs.ext4 /persistent/var_lib_docker.img > /dev/null 2>&1
fi

# verify TMPDIR configuration
if [ $(stat --file-system --format=%T $TMPDIR) != tmpfs ]; then
    echo "For better performance, consider mounting a tmpfs on $TMPDIR like this: \`docker run --tmpfs $TMPDIR:rw,nosuid,nodev,exec,size=8g\`"
fi

#start the uml kernel with docker inside
echo "DIUID_DOCKERD_FLAGS=\"$DIUID_DOCKERD_FLAGS\"" > /tmp/env

# Get docker group from DIUID_DOCKERD_FLAGS
DIUID_DOCKERD_GROUP='docker'
DIUID_DOCKERD_OPTS=`getopt -q -o G: --long group: -n 'getopt' -- $DIUID_DOCKERD_FLAGS`
eval set -- "$DIUID_DOCKERD_OPTS"
while true; do
  case "$1" in
	-G|--group ) DIUID_DOCKERD_GROUP="$2"; shift 2 ;;
    -- ) shift; break ;;
    * ) break ;;
  esac
done
echo "DIUID_DOCKERD_GROUP=\"$DIUID_DOCKERD_GROUP\"" >> /tmp/env

/sbin/start-stop-daemon --start --background --make-pidfile --pidfile /tmp/kernel.pid --exec /bin/bash -- -c "exec /kernel.sh > /tmp/kernel.log 2>&1"

echo -n "waiting for dockerd "
while true; do
	if docker version 2>/dev/null >/dev/null; then
		echo ""
		break
	fi
	if ! /sbin/start-stop-daemon --status --pidfile /tmp/kernel.pid; then
		echo ""
		echo failed to start uml kernel:
		cat /tmp/kernel.log
		exit 1
	fi

	echo -n "."
	sleep 0.5
done

echo "Executing \"$ARGS\""
exec $ARGS