Installation guide with CentOS 7

Recommended environment

For the sake of simplicity, this guide assumes the following environment:

• CentOS 7 (operating system)
• Python 3.6
• Gunicorn (Python WSGI server)
• Nginx (static content server and reverse proxy)
• SQLite (database)

There is nothing to prevent you from using NEMO in a different environment, however, we have only tested NEMO in this production environment.

Install the Python 3.6 interpreter

Download and install the following packages in order to compile Python. Also create a nemo user which will run the NEMO application and web server.

Execute these commands with root privileges:

yum -y install gcc wget sqlite-devel openssl-devel git
useradd -c "NEMO" nemo

Execute these commands as the nemo user (unprivileged):

To compile and install Python...

cd /home/nemo
wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tgz
tar xf Python-3.6.2.tgz
cd Python-3.6.2/
./configure --prefix=/home/nemo/python
make
make install
cd /home/nemo
rm -rf Python-3.6.2 Python-3.6.2.tgz

Python is now installed in the /home/nemo/python/ directory.

Configure environment variables

You'll need to set some environment variables to specify the location of the Python interpreter, and where NEMO should read its settings from.

All Django projects (including NEMO) read in their settings from one important file: settings.py. The Django documentation states you should specify the settings location using the environment variable DJANGO_SETTINGS_MODULE. The value of DJANGO_SETTINGS_MODULE should be in Python path syntax.

Additionally, the settings file should be on the Python import search path. You will probably also need to set PYTHONPATH to the directory that contains the settings file. For example, if the file settings.py resides in the directory /home/nemo/, you would set PYTHONPATH=/home/nemo and DJANGO_SETTINGS_MODULE=settings.

Edit /home/nemo/.bashrc to set environment variables to point to the correct Python interpreter and settings by adding:

PATH=/home/nemo/python/bin:$PATH
PYTHONPATH=/home/nemo
DJANGO_SETTINGS_MODULE="settings"
export PATH PYTHONPATH DJANGO_SETTINGS_MODULE

Refresh the environment variables by closing the bash terminal and reopening it as the nemo user. Ensure the proper Python interpreter is available in your PATH environment variable using which python3... the first line of output should be /home/nemo/python/bin.

Install NEMO

pip3 install git+https://github.com/usnistgov/NEMO.git

Set up filesystem and external dependencies

You will need a place to store media and static content that NEMO uses:

cd /home/nemo
mkdir media static

You'll need to generate a secret key which is used by Django for password and session hashing. The NEMO package comes with an executable script that assists with this. nemo generate_secret_key will output a random 50 character key to standard output, which can be redirected to a file.

nemo generate_secret_key > django_secret_key.txt

Reference this file in your settings.py by assigning
SECRET_KEY = get_file_contents('/path/to/django_secret_key.txt').

Create the database

cd /home/nemo/
python3 manage.py makemigrations NEMO
python3 manage.py migrate

"Run once" command

To start NEMO on the command line: gunicorn NEMO.wsgi:application

This will serve NEMO on the default address for Gunicorn: 127.0.0.1:8000.

To test NEMO by fetching the root URL, use: curl 127.0.0.1:8000 or curl localhost:8000

TODO: add instructions for

• systemd configuration (automatic startup on boot, and more)
• ensure the firewall is open on TCP port 443
• Nginx reverse proxy and static content server