Getting Started¶
This tutorial will guide you through setting up your first project using dh-virtualenv. Having some knowledge on how Debian packages work might help, but it is not a mandatory requirement when working on simple projects.
You also need some basic build tools, so you should install these packages:
sudo apt-get install build-essential debhelper devscripts equivs
These are only required on the build host, not the target hosts you later install the built packages on.
Step 1: Install dh-virtualenv¶
In order to use it, you need to install dh-virtualenv as a debhelper add-on on the build host. For Debian and Ubuntu, there are pre-built packages for the 1.0 version available – note that some of this info might get outdated over time, so take extra care to check the version numbers you’re actually getting.
The following paragraphs describe the various installation options, including building from source when your specific environment provides no packages or only older versions. Using pre-1.0 versions might be possible, but you don’t get all features described in this document, and not all projects using dh-virtualenv might work with older versions (check their documentation).
To install on Jessie (Debian stable) from their package repositories, use these commands:
echo "deb http://ftp.debian.org/debian jessie-backports main" \
| sudo tee /etc/apt/sources.list.d/jessie-backports.list >/dev/null
sudo apt-get update -qq
sudo apt-get install -t jessie-backports dh-virtualenv
Note that only jessie-backports offers the 1.0 version.
Newer versions (Stretch and Sid) provide 1.0 out-of-the-box.
In the official Ubuntu repositories, Zesty provides a package
that works on older releases too. So on Zesty use a standard apt-get install,
and on older releases do this:
( cd /tmp && curl -LO "http://mirrors.kernel.org/ubuntu/pool/universe/d/dh-virtualenv/dh-virtualenv_1.0-1_all.deb" )
sudo dpkg -i /tmp/dh-virtualenv_1.0-1_all.deb
Another option to check out for Ubuntu is this PPA, maintained by the author.
For all other systems you have to build and install the tool yourself. Steps to do that, after you have cloned the repository, are:
sudo apt-get install devscripts python-virtualenv python-sphinx python-sphinx-rtd-theme git equivs # Install needed packages
git clone https://github.com/spotify/dh-virtualenv.git # Clone Git repository
cd dh-virtualenv # Move into the repository
sudo mk-build-deps -ri # This will install build dependencies
dpkg-buildpackage -us -uc -b # Build the *dh-virtualenv* package
# and finally, install it (you might have to solve some
# dependencies when doing this):
sudo dpkg -i ../dh-virtualenv_<version>.deb
Step 2: Set up Debian packaging¶
Grab your favourite Python project you want to use dh-virtualenv
with and set it up. Only requirement is that your project has a
somewhat sane setup.py and requirements listed in a
requirements.txt file. Note however that defining any requirements
is not mandatory.
Next you need to define the Debian packaging for your software. To do
this, create a directory called debian in the project root.
To be able to build a debian package, a few files are needed. First, we need to define the compatibility level of the project. For this, do:
echo "9" > debian/compat
The 9 is a magic number for latest compatibility level, but we don’t
need to worry about that. Next we need a file that tells what our
project is about, a file called control. Enter a following
debian/control file:
Source: my-awesome-python-software
Section: python
Priority: extra
Maintainer: Matt Maintainer <matt@example.com>
Build-Depends: debhelper (>= 9), python, dh-virtualenv (>= 0.8)
Standards-Version: 3.9.5
Package: my-awesome-python-software
Architecture: any
Pre-Depends: dpkg (>= 1.16.1), python2.7 | python2.6, ${misc:Pre-Depends}
Depends: ${misc:Depends}
Description: really neat package!
second line can contain extra information about it.
The control file is used to define the build dependencies, so if you
are building a package that requires for example lxml, make sure
you define libxml2-dev in Build-Depends etc.
Depends in the lower section is used to define run-time dependencies.
Following the example above, in case of lxml you would add libxml2
in to the Depends field.
To help keeping your installed virtualenv in sync with the host’s Python
interpreter in case of updates, create a file named
debian/«pkgname».triggers, where «pkgname» is what you
named your package in the control file. It triggers a special script
whenever the Python binary changes; don’t worry, that script is provided
by dh-virtualenv automatically.
«pkgname».triggers
# Register interest in Python interpreter changes (Python 2 for now); and
# don't make the Python package dependent on the virtualenv package
# processing (noawait)
interest-noawait /usr/bin/python2.6
interest-noawait /usr/bin/python2.7
# Also provide a symbolic trigger for all dh-virtualenv packages
interest dh-virtualenv-interpreter-update
Note that if you provide a custom postinst script with your package,
then don’t forget to put the #DEBHELPER# marker into it, else the trigger
script will be missing.
Next, we need a changelog file. It is basically a documentation of
changes in your package plus the source for version number for Debian
package builder. Here’s a short sample changelog to be entered in
debian/changelog:
my-awesome-python-software (0.1-1) unstable; urgency=low
* Initial public release
-- Matt Maintainer <matt@example.com> Fri, 01 Nov 2013 17:00:00 +0200
You don’t need to create this file by hand, a handy tool called
dch exists for entering new changelog entries.
Now, last bit is left, which is the debian/rules file. This file
is basically a Makefile that Debian uses to build the package. Content
for that is fairly straightforward:
#!/usr/bin/make -f
%:
dh $@ --with python-virtualenv
And there we go, debianization of your new package is ready!
Step 3: Build your project¶
Now you can just build your project by running dpkg-buildpackage -us
-uc. Enjoy your newly baked dh-virtualenv backed project! ☺