...
services:
  appserver:
    build_as_root:
      - apt-get update -y && apt-get install -y memcached libmemcached-tools
      - echo "#!/bin/sh\n/etc/init.d/memcached start\nexit 0" > /scripts/200-memcache-start
      - chmod u=rwx,g=rx,o=rx /scripts/200-memcache-start && chown www-data:www-data /scripts/200-memcache-start
      - sed -i 's/-m 64/-m 256/g'  /etc/memcached.conf && echo '-o modern' >> /etc/memcached.conf
      - sh /scripts/200-memcache-start
...