Travis CI Deployment
It can be handy to have code run when commits are pushed to GitHub – you can do lots of things with this, but commonly it is used to run unit tests, build a docker image, or deploy something. In this example we will deploy this website to github pages using Travis-CI (which is free for open repositories).
Step by step
Enable Travis for your Github account via the website https://travis-ci.org/. It will guide you through the process of activating a repository. For private repositories you will have to pay money and use the website https://travis-ci.com/. The rest of this guide assumes that you have activated Travis for your personal account or organisation.
Choose a language
Travis will run based on instructions stored in a
.travis.yml file. See Travis documentation for more information. We specify that we are using
R and that we want to cache packages.
‘Caching’ will speed up the build considerably, by reusing compiled dependencies from one build in subsequent builds. Travis has to compile packages because pre-compiled ‘binary’ packages are not available for the Linux operating system, which is what Travis runs on. A recent website was built 10 times faster by using caching (3 minutes rather than 30 minutes).
# cache packages so that each build doesn't require installation...
# Install packages we need
2. Generate an SSH key
Each time we push or pull from GitHub we will use an ssh key generated just for this repo. Don’t use your personal ssh key. To create a new key, use the command below, and make a note of where you save the key.
ssh-keygen -t rsa -b 4096 -C "firstname.lastname@example.org"
>Generating public/private rsa key pair.
>Enter file in which to save the key (/Users/will.bowditch/.ssh/id_rsa): />Users/will.bowditch/projects/rap-website/deploy_key
Encrypt the key
We don’t want people to be able to read the key, so we use travis to encrypt it (you’ll need to install the
travis command line tool). The command
travis encrypt-file deploy_key adds a line to the
.travis.yml file that tells Travis to use the encrypted key. If you run the command
travis encrypt-file deploy_key --add then you can skip step 4.
travis encrypt-file deploy_key
> encrypting deploy_key for ukgovdatascience/rap-website
> storing result as deploy_key.enc
> DANGER ZONE: Override existing deploy_key.enc? |no| yes
> storing secure env variables for decryption
> Please add the following to your build script(before_install stage in your >.travis.yml, for instance):
> openssl aes-256-cbc -K $encrypted_516b420c1ae6_key-iv $encrypted_516b420c1ae6_iv -in deploy_key.enc-out deploy_key -d
> Pro Tip: You can add it automatically by running with --add.
> Make sure to add deploy_key.enc to the git repository.
> Make sure not to add deploy_key to the git repository.
> Commit all changes to your .travis.yml.
If you store unencrypted key
deploy_key in the repo folder, then name it in
.gitignore to avoid accidentally publishing it on GitHub. It doesn’t matter if you lose the key because you can create a new one.
4. Tell Travis to decrypt the key
If you ran the command
travis encrypt-file deploy_key --add in the previous step (note the
--add) then you can skip this step. If you ran the command
travis encrypt-file deploy_key then it it will have shown you an
openssl command. Add this command to the
.travis.yml file. This command uses two environment variables stored by travis to decrypt the ssh key.
# Decrypt the deployment key, used to push the result to the repo
- openssl aes-256-cbc -K $encrypted_516b420c1ae6_key-iv $encrypted_516b420c1ae6_iv -in deploy_key.enc-out deploy_key -d
Note that, with this setup, the decryption will happen for every run of Travis regardless of if you actually need the deployment key. In some scenarios this can be a problem. For example, if you have a pull request from a forked repo, Travis will not have permission to access the encrypted enviroment variables and the build will fail. To get around this, you can move the
openssl command into a script that only runs when deployment is needed (for example, only when on the master branch
if [[ $TRAVIS_BRANCH == 'master' ]]).
5. Add the key to GitHub
Add the ssh key to the repository as a deployment key. Find the place to put it on GitHub by navigating to
Repo > Settings > Deploy keys > Add deploy key. There, paste in the contents of the
deploy_key file you generated earlier.
on OS X you can use
cat deploy_key.pub | pbcopy to copy the key to the clipboard.
Tick allow write access if you want the key to have permission to push to the repo. This is the case if you are using Travis to render a website and publish it in a
/docs folder or
6. Tell Travis what to do
Tell Travis what scripts to run on each commit. To allow them to run they need to be made executable with the command
chmod +x. The scripts can do anything. In this example the scripts tell Travis to build a website using rmarkdown and push it to the
gh-pages branch on github. GitHub will then publish the website.
Travis has several environment variables to control whether scripts run only on pull requests or on certain branches. Below we are only going to run the deploy script if it isn’t a pull request and is on the master branch. Put this either in the
.travis.yml file or in the bash scripts (see the file
# Make bash scripts executable, so they can be run later.
- chmod +x ./_build.sh
- chmod +x ./_deploy.sh
- if [ "$TRAVIS_PULL_REQUEST" = "false" ]; then bash ./_deploy.sh; else echo "PR so
not deploying"; fi
# Build the site in `/site`
Rscript -e "rmarkdown::render_site(input='site')"
# Start ssh agent and add key
eval "$(ssh-agent -s)" # Start the ssh agent
chmod 600 deploy_key
# Only publish to gh-pages if on the master branch
if [[ $TRAVIS_BRANCH == 'master' ]]
# configure your name and email if you have not done so
git config --global user.email "email@example.com"
git config --global user.name "your_github_username"
# clone the repository to the book-output directory
git clone -b gh-pages \
# Remove everything from this branch.
git rm -rf *
# Copy the new site, add all, and commit!
cp -r ../site/docs/* ./
git add --all *
git commit -m "Travis built book"
git push -q origin gh-pages
echo "Not publishing as not in MASTER branch"