# RUNLEVEL=1 apt-get install nginx

Sadly this doesn't work in newer versions of Debian/Ubuntu, the official way is to use the policy helper script /usr/sbin/policy-rc.d and return a 101 exit code. This is a a bit more inconvenient - having to temporarily create this file only to remove it after installing the package.

Fortunately there is an alternative - policyrcd-script-zg2. Install the package:

$ sudo apt-get install policyrcd-script-zg2

Create a new script which returns a 101 exit code, I've created it as /usr/local/sbin/policy-donotstart:

#!/bin/sh
exit 101

Then make it executable:

$ sudo chmod 755 /usr/local/sbin/policy-donotstart

When installing packages where you don't want the service to immediately start, use the POLICYRCD environment variable:

# POLICYRCD=/usr/local/sbin/policy-donotstart apt-get install nginx

The service will install, but you'll a message similar to:

invoke-rc.d: policy-rc.d denied execution of start.

For Ansible, you can add environment variables to any task:

- name: Install nsd
  apt: pkg=nsd install_recommends=no
  environment:
    POLICYRCD: /usr/local/sbin/policy-donotstart

Now you can safely install a package, configure it, and then start it once you've got all the correct files in place - all with a convenient environment variable.

These days you could use containers to deploy bleeding edge applications with all the new stuff bundled inside, maybe with either Docker or rkt. However in this post we'll be going through a couple of available APT repositories to help modernise a slightly older distribution.

Python

As of October 2016, Python 3.5 is the latest stable version of Python. It's supported in Django 1.8 to 1.10, and for anyone wanting to develop an app for the long term - going for Python 2.7 at this point in time is a dead end. Ubuntu Trusty only has Python 2.7 and 3.4, although 3.4 is well supported - we want to try and go for the latest possible Python version.

Deadsnakes

The Old and New Python Versions repository (or deadsnakes) provides multiple Python versions which aren't included in a particular version of Ubuntu. Consider the support of this repository carefully, as it isn't an official repo (stick with Python 3.4 if this bothers you).

Installation is quick and easy:

$ sudo add-apt-repository ppa:fkrull/deadsnakes
$ sudo apt-get update
$ sudo apt-get install python3.5

As deadsnakes provides even more versions - we could also install Python 3.3 as well, which could help in testing code under multiple Python versions with tox.

PostgreSQL

Ubuntu Trusty comes with PostgreSQL 9.3, which is missing JSONB support. So if we want the JSONField which is new since Django 1.9 - we'll need a more modern version of Postgres. As of October 2016 the latest release of Postgres is 9.6 - which is what we want to aim for.

PostgreSQL Apt Repository

Fortunately postgresql.org provides official packages of all the supported Postgres versions for quite a few supported distributions. As this is provided by the official Postgres site, packages are updated with every new release - so support is good.

To install:

$ sudo add-apt-repository "deb http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg main"
$ curl -sL https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
$ sudo apt-get update
$ sudo apt-get install postgresql-9.6

Now we can use JSONField thanks to the updated Postgres.

Conclusion

Just because you're stuck on an older release of Ubuntu doesn't mean you're stuck with all the old tools - go upgrade!