Installing Passenger + Nginx on a Digital Ocean production server
for Python apps + Red Hat 6 / CentOS 6 (with RPM)

On this page, we will install Passenger. After installing Passenger we can begin with deploying the app.

Step 1: upgrade your kernel, or disable SELinux

The first thing you need to do is to check on three things:

1. Which Passenger version will be installed? You can check with curl -s https://www.phusionpassenger.com/latest_stable_version.json | ruby -rjson -e 'p JSON.parse(STDIN.read)["version"]'.
2. Which kernel version are you running? You can find out by running uname -r.
3. Is SELinux enabled? You can find out by running grep SELINUX /etc/selinux/config. If it says "enforcing" or "permissive", then SELinux is enabled. If it says "disabled", then SELinux is disabled.

If you are installing Passenger 5.1 or later, or if your kernel version was already at least 2.6.39, or if SELinux was already disabled, then you can skip to the next step.

If SELinux is enabled, then Passenger versions prior to 5.1 require kernel >= 2.6.39. Passenger 5.1 has removed this requirement. If your kernel is not recent enough, then there are two things you can do:

1. Disable SELinux completely. Edit /etc/selinux/config, set SELINUX=disabled and reboot. Note that merely setting SELinux to permissive mode is not sufficient.

   -OR-

2. Upgrade your kernel to at least 2.6.39.

Step 2: enable EPEL

The instructions differ depending on whether you are on Red Hat or CentOS. The second step is only necessary on Red Hat.

$ sudo yum install -y epel-release yum-utils
$ sudo yum-config-manager --enable epel
$ sudo yum clean all && sudo yum update -y

$ sudo subscription-manager register --username $RHN_USERNAME --password $RHN_PASSWORD
$ POOL=`sudo subscription-manager list --available --all | sed '/^Pool ID:/!d;s/^.*: *//'`
$ sudo subscription-manager attach --pool="$POOL"
$ sudo subscription-manager repos --enable rhel-6-server-optional-rpms

Step 3: repair potential system issues

These commands will fix common issues that prevent yum from installing Passenger

# Ensure curl and nss/openssl are sufficiently up-to-date to talk to the repo
sudo yum update -y

date
# if the output of date is wrong, please follow these instructions to install ntp
sudo yum install -y ntp
sudo chkconfig ntpd on
sudo ntpdate pool.ntp.org
sudo service ntpd start

Step 4: install Passenger packages

These commands will install Passenger Nginx through Phusion's YUM repository. If you already had Nginx installed, then these commands will upgrade Nginx to Phusion's version (with Passenger compiled in).

# Install various prerequisites
sudo yum install -y pygpgme curl

# Add our el6 YUM repository
sudo curl --fail -sSLo /etc/yum.repos.d/passenger.repo https://oss-binaries.phusionpassenger.com/yum/definitions/el-passenger.repo

# Install Passenger Nginx
sudo yum install -y nginx passenger || sudo yum-config-manager --enable cr && sudo yum install -y nginx passenger

Step 5: enable the Passenger Nginx module and restart Nginx

Edit /etc/nginx/conf.d/passenger.conf and uncomment passenger_root, passenger_ruby and passenger_instance_registry_dir. For example, you may see this:

# passenger_root /some-filename/locations.ini;
# passenger_ruby /usr/bin/ruby;
# passenger_instance_registry_dir /var/run/passenger-instreg;

Remove the '#' characters, like this:

passenger_root /some-filename/locations.ini;
passenger_ruby /usr/bin/ruby;
passenger_instance_registry_dir /var/run/passenger-instreg;

$ passenger-config --root
/some-filename/locations.ini

passenger_root /some-filename/locations.ini;
passenger_instance_registry_dir /var/run/passenger-instreg;

When you are finished with this step, restart Nginx:

$ sudo service nginx restart

Step 6: check installation

After installation, please validate the install by running sudo /usr/bin/passenger-config validate-install. For example:

$ sudo /usr/bin/passenger-config validate-install
 * Checking whether this Phusion Passenger install is in PATH... ✓
 * Checking whether there are no other Phusion Passenger installations... ✓

All checks should pass. If any of the checks do not pass, please follow the suggestions on screen.

Finally, check whether Nginx has started the Passenger core processes. Run sudo /usr/sbin/passenger-memory-stats. You should see Nginx processes as well as Passenger processes. For example:

$ sudo /usr/sbin/passenger-memory-stats
Version: 5.0.8
Date   : 2015-05-28 08:46:20 +0200
...

---------- Nginx processes ----------
PID    PPID   VMSize   Private  Name
-------------------------------------
12443  4814   60.8 MB  0.2 MB   nginx: master process /usr/sbin/nginx
12538  12443  64.9 MB  5.0 MB   nginx: worker process
### Processes: 3
### Total private dirty RSS: 5.56 MB

----- Passenger processes ------
PID    VMSize    Private   Name
--------------------------------
12517  83.2 MB   0.6 MB    PassengerAgent watchdog
12520  266.0 MB  3.4 MB    PassengerAgent server
12531  149.5 MB  1.4 MB    PassengerAgent logger
...

If you do not see any Nginx processes or Passenger processes, then you probably have some kind of installation problem or configuration problem. Please refer to the troubleshooting guide.

Step 7: update regularly

Nginx updates, Passenger updates and system updates are delivered through the YUM package manager regularly. You should run the following command regularly to keep them up to date:

$ sudo yum update

After an update, you should restart Nginx. Doing so will automatically restart Passenger too.

Next step

Now that you have installed Passenger, you are ready to deploy your Python application on the production server!

Continue: Deploy app »