Deploy with ‘Git Push’

by in Tips & Tutorials
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Single command deploys are awesome. When setting up a testing or production server, I always setup a script to deploy in a single command because it makes life easier and encourages frequent deploys.

There are many different ways of setting up one click deploys. This tutorial covers how to setup a git postcommit hook that deploys on git push prod, which is pretty simple to get started with, but won’t scale well once you start running multiple app servers. For alternatives, you might have a look at Fabric or Capistrano.

Setup the git repo on the server

If you don’t already have git installed on the server, ssh in and do a

sudo apt-get install git

Now we want to create a git user:

sudo adduser \
    --system \
    --shell /bin/sh \
    --gecos 'git version control' \
    --group \
    --disabled-password \
    --home /var/git \
    git

And append your ssh public key to the git user’s list of authorized keys located at /var/git/.ssh/authorized_keys, creating the file if necessary.

Now let’s create the repository:

cd /var/git
sudo -u git mkdir <repo-name>.git
cd <repo-name>.git
sudo -u git git init --bare

The repository here is bare so that it can accept pushes. See this discussion of bare vs. non-bare repos if you are interested in learning more.

Create a hook

OK so now we want to create the script that will run after a git push is received.

Create a file called /var/git/<repo-name>.git/hooks/post-receive and give it these contents:

#!/bin/bash
export GIT_WORK_TREE=/var/www/<app-name>/project/
git checkout -f

The above assumes that your server is setup with /var/www/<app-name>/project/ as the location where your app server will be looking for your code files.

Add execute permissions and make sure it is owned by git:

sudo chmod u+x hooks/post-receive
sudo chown git:git hooks/post-receive

Handle permissions

The post receive script will be run as git, so we need to make sure that the git user has permissions to write to the GIT_WORK_TREE, and also that the server can read and write from those directories. To handle this, lets make git a member of the nginx group, and then have the post receive script touch up the file permissions after checkout.

sudo usermod -a -G nginx $USER

Then edit the script to look like this:

#!/bin/bash                                                                     

# Checkout the repo.                                                            
export GIT_WORK_TREE=/var/www/<app-name>/project/
git checkout -f

# Fix up permissions.
cd /var/www/<app-name>                                                           
chmod -R g+w project/*
chown -R git:nginx project/*

Prepare development box

Now on your development machine, add the new remote repository and push to it:

git remote add prod ssh://git@<server>/var/git/<repo-name>.git
git push prod master

Other deploy tasks

Often there will be other tasks that have to happen during the deploy. Here is an example of another post-receive hook script that I use for one of my Django projects. It collects the static files to prepare them to be served via nginx, runs the database migrations, and installs any new python requirements.

#!/bin/bash                                                                     

# Checkout the repo.                                                            
export GIT_WORK_TREE=/var/www/<app-name>/project/
git checkout -f

# Fix up permissions.                                                           
cd $GIT_WORK_TREE
chmod -R g+w *py
chown -R git:nginx *py

source ../env/bin/activate

# Collect static files                                                          
./manage.py collectstatic --noinput -v 0

# Handle DB Migrations                                                          
./manage.py syncdb --migrate -v 0

# Update requirements                                                           
pip install -q -r requirements.txt

deactivate

So there it is – a quick way to setup one touch deploys with git.

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# November 5, 2012 2 Comments