Firewall (UFW)

You should set up the firewall. It is installed but inactive by default.

You can check the status and available applications using the following commands:

ufw status

ufw app list

Before enabling the firewall, you should allow incoming SSH requests (port 22 by default) to avoid being locked out. You should also allow incoming requests for HTTP (port 80) and HTTPS (port 443). This can be done using the following commands:

ufw allow openssh

ufw allow http

ufw allow https

ufw enable

Firewall rules can be removed using the following command:

ufw delete allow <RULE>

The firewall can be disabled completely using the following command:

ufw disable

SSH

If necessary, you can edit the SSH configuration in /etc/ssh/sshd_config and then restart the sshd service using the following command:

service sshd restart

For example, you might want to change the default port for incoming SSH connections using the following setting:

Port <PORT>

You could allow password authentication:

PasswordAuthentication yes

And you probably want to disable remote root login via SSH:

PermitRootLogin no

Timezone

Check the current timezone:

timedatectl

List available timezones:

timedatectl list-timezones

Set the timezone:

timedatectl set-timezone <TIMEZONE>

If necessary, enable NTP synchronisation:

timedatectl set-ntp on

Swap File

Create a swap file using the following commands:

fallocate -l 4G /swapfile

chmod 600 /swapfile

mkswap /swapfile

swapon /swapfile

echo "/swapfile swap swap defaults 0 0" >> /etc/fstab

Core Packages

An Ubuntu 18.04 droplet from DigitalOcean is pretty bare-bones but should have the following useful packages already installed:

• git (v 2.17.1)

• python3 (v 3.6.8)

• ssh

• ufw

• vim

Update the system packages:

apt-get update

apt-get upgrade

apt dist-upgrade

Next, you'll want to install the core packages and dependencies for running a Rails application using the following command:

apt-get install build-essential libcurl4-openssl-dev libffi-dev libreadline-dev libssl-dev libxml2-dev libxslt1-dev libyaml-dev software-properties-common zlib1g-dev

Git

Git should already be installed. If it isn't, you can install it using the following command:

apt-get install git

Node.js and Yarn

Install Node.js and Yarn using the following commands:

curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -

echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list

apt-get update

apt-get install nodejs yarn

Nginx

Install Nginx:

apt-get install nginx

After installing, Nginx will start automatically. You can check using the following command:

systemctl status nginx

You can now serve static files from /var/www/html and access them in a web browser via the IP address of the deployment server.

In addition, the configuration for the default site can be edited found at /etc/nginx/sites-enabled/default.

SQLite

Install SQLite:

apt-get install sqlite3 libsqlite3-dev

PostgreSQL

Install PostgreSQL:

apt-get install postgresql postgresql-contrib

You can switch to the postgres user and launch the psql prompt using the following command:

sudo -u postgres psql

You can close the psql prompt by typing \q.

If necessary, while logged in as the postgres user, you can create a new role using the following command:

createuser -d <ROLE>

To list all roles, run the following command from the psql prompt:

\du