Install a Mastodon Server on Ubuntu 20.04

Mastodon is an open-source and decentralized micro-blogging platform. Like Twitter, it lets users follow other users and post text, photos, and video content. Mastodon also allows you to create a non-profit social network based on open web standards and principles. Unlike Twitter, Mastodon is decentralized, meaning that its content is not maintained by a central authority.

What sets the Mastodon platform apart is its federated approach to social networking. Each Mastodon instance operates independently — anyone can create an instance and build their community. But users from different instances can still follow each other, share content, and communicate.

Mastodon participates in the Fediverse, a collection of social networks and other websites that communicate using the ActivityPub protocol. That allows different Mastodon instances to communicate, and also allows other platforms in the Fediverse to communicate with Mastodon.

Mastodon servers range in size from small private instances to massive public instances and typically center on specific interests or shared principles. The biggest Mastodon server is Mastodon.social, a general-interest server created by the developers of the Mastodon platform. It has over 540,000 users and boasts a thorough Code of Conduct.

1. If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.

2. Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.

3. Complete the steps in the Add DNS Records section to register a domain name to point to your Mastodon instance.

4. Prepare an SMTP server for Mastodon to send email notifications to users when they register for the site, get a follower, receive a message, and for other Mastodon activity.

   • You can create your SMTP server — and even host it on the same machine as your Mastodon server — by following the Email with Postfix, Dovecot, and MySQL guide.

     Note

     This guide uses PostgreSQL database as a backend for Mastodon. You can setup the SMTP server with PostgreSQL database instead of MySQL.

   • Alternatively, you can use a third-party SMTP service. This guide provides instructions for using Mailgun as your SMTP provider.

5. Replace occurrences of example.com in this guide with the domain name you are using for your Mastodon instance.

Note

This guide is written for non-root users. Commands that require elevated privileges are prefixed with sudo. If you’re not familiar with the sudo command, see the Linux Users and Groups guide.

Mastodon can be installed using its included Docker Compose file. Docker Compose installs and runs all of the requisites for the Mastodon environment in Docker containers. If you have not used Docker before, it is recommended that you review the following guides:

• Introduction to Docker
• How to Use Docker Compose

To install Docker CE (Community Edition), follow the instructions within one of the guides below:

• Installing and Using Docker on Ubuntu and Debian

• Installing and Using Docker on CentOS and Fedora

For complete instructions on even more Linux distributions, reference the Install Docker Engine section of Docker’s official documentation.

1. Download the latest version of Docker Compose. Check the releases page and replace 1.25.4 in the command below with the version tagged as Latest release:

   sudo curl -L https://github.com/docker/compose/releases/download/1.25.4/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose

2. Set file permissions:

   sudo chmod +x /usr/local/bin/docker-compose

1. Clone the Mastodon Git repository into the home directory, and change it into the resulting Mastodon directory.

   cd ~/
   git clone https://github.com/mastodon/mastodon.git
   cd mastodon

   Unless otherwise stated, all the Docker Compose-related commands to be run in this directory.

1. Using your preferred text editor, open the docker-compose.yml file located in the mastodon directory.

2. Comment out the build lines (adding # in front of each), and append a release number to the end of each image: tootsuite/mastodon line as here: tootsuite/mastodon:v3.3.0.

   Although you can use latest as the release, it is recommended that you select a specific release number. The Mastodon GitHub page provides a chronological list of Mastodon releases.

3. In the db section, add the following beneath the image line. Replace password with a password you would like to use for the PostgreSQL database that operates on the Mastodon backend.

   File: docker-compose.yml

   1 2 3 4

   environment: POSTGRES_PASSWORD: password POSTGRES_DB: mastodon_production POSTGRES_USER: mastodon

4. The resulting docker-compose.yml file should resemble the example Docker file.

5. Copy the .env.production.sample file (which is in the current mastodon directory) to create a new environment configuration file.

   cp .env.production.sample .env.production

6. Use Docker and Mastodon to generate a new value for the SECRET_KEY_BASE setting:

   SECRET_KEY_BASE=$(docker-compose run --rm web bundle exec rake secret)

   This creates a string of random characters. If you encounter an error in the next step, run the command again to generate another string.

7. Insert the SECRET_KEY_BASE setting into .env.production using the sed command:

   sed -i -e "s/SECRET_KEY_BASE=/&${SECRET_KEY_BASE}/" .env.production

8. Combine the previous two actions into one step to set a value for the OTP_SECRET setting in .env.production:

   sed -i "s/OTP_SECRET=$/&$(docker-compose run --rm web bundle exec rake secret)/" .env.production

9. Generate values for VAPID_PRIVATE_KEY and VAPID_PUBLIC_KEYsettings:

   docker-compose run --rm web bundle exec rake mastodon:webpush:generate_vapid_key

10. Copy the output from the previous command, open .env.production in your text editor, and paste the command output into the two lines for VAPID_PRIVATE_KEY and VAPID_PUBLIC_KEY.

11. Fill out the remaining fields of the .env.production file:

    • LOCAL_DOMAIN: Enter your Mastodon server’s domain name.

    • DB_PASS: Enter the password you set for the database in the docker-compose.yml file.

    • Enter mastodon_db_1 for DB_HOST and mastodon_redis_1 for REDIS_HOST. In both of these values, mastodon corresponds to the name of the Mastodon base folder.

    • Fill out the SMTP fields with the information from your SMTP provider. If you set up your SMTP server, use its domain name for SMTP_SERVER and add the following lines:

      File: .env.production

      1 2	SMTP_AUTH_METHOD=plain SMTP_OPENSSL_VERIFY_MODE=none

    Comment out the sections denoted as “optional” by adding a # before each line in the section.

12. The resulting .env.production file should resemble the example environment file.

1. Build the Docker Compose environment.

   docker-compose build

2. Give ownership of the Mastodon public directory to user 991. This is the default user ID for Mastodon, and this command ensures that it has the necessary permissions.

   sudo chown -R 991:991 public

3. Run Mastodon’s Docker Compose setup script. You are prompted to enter information about the Docker Compose services and the Mastodon instance.

   docker-compose run --rm web bundle exec rake mastodon:setup

   • Many prompts repeat fields you completed in the .env.production file. Make sure to enter the same information here as you entered in the file.

   • When prompted to create a Mastodon admin user account, choose to do so (Y). Enter the username, password, and email address you would like to use to access the account.

   • For any other prompts, enter the default values by pressing Enter.

1. Start the Docker Compose services.

   docker-compose up -d

2. Unless manually stopped, the Docker Compose services begin running automatically at system startup. Run the following command to manually stop the Docker Compose services:

   docker-compose down

1. Allow HTTP and HTTPS connection on the system’s firewall.

   sudo ufw allow http
   sudo ufw allow https
   sudo ufw reload

2. Install NGINX, which proxies requests to your Mastodon server.

   sudo apt install nginx

3. Copy the nginx.conf file included with the Mastodon installation to the sites-available NGINX folder; use your Mastodon domain name instead of example.com in the file name:

   sudo cp ~/mastodon/dist/nginx.conf /etc/nginx/sites-available/example.com.conf

4. Open the example.com.conf file with your preferred text editor, and replace all instances of example.com with the domain name for your Mastodon site. This domain name must match the one you used to set up Docker Compose for Mastodon.

5. Create a symbolic link of this file in the sites-enabled NGINX folder.

   cd /etc/nginx/sites-enabled
   sudo ln -s ../sites-available/example.com.conf

Mastodon is served over HTTPS, so you need an SSL/TLS certificate. This guide uses Certbot to request and downloads a free certificate from Let’s Encrypt.

1. Update the Snap app store. Snap provides application bundles that work across major Linux distributions and comes by default with all Ubuntu releases since 16.04:

   sudo snap install core && sudo snap refresh core

2. Ensure that any existing Certbot installation is removed.

   sudo apt remove certbot

3. Install Certbot.

   sudo snap install --classic certbot

4. Download a certificate for your site.

   sudo certbot certonly --nginx

   Certbot prompts you to select from the NGINX sites configured on your machine. Select the one with the domain name you set up for your Mastodon instance.

5. Certbot includes a chron job that automatically renews your certificate before it expires. You can test the automatic renewal with the following command.

   sudo certbot renew --dry-run

6. Open the /etc/nginx/sites-available/example.com.conf file again, and un-comment the ssl_certificate and ssl_certificate_key lines.

7. Restart the NGINX server.

   sudo systemctl restart nginx

1. In a web browser, navigate to your Mastodon site’s domain. You should see the Mastodon login page, where you can log in as the admin user you created earlier or create a new user.

2. You can navigate to your instance’s administration page by navigating to example.com/admin/settings/edit. The administration page allows you to alter the look, feel, and behavior of your instance.

3. If your instance is running but having issues, you can troubleshoot them from the Sidekiq dashboard. Either select Sidekiq from the administration menu or navigate to example.com/sidekiq to see the dashboard.

To learn more about Mastodon, check out the official Mastodon blog with news and articles related to Mastodon. You can engage with the Mastodon administrative community on Mastodon’s discussion forum, where you can peruse conversations about technical issues and community governance.

When you are ready to make your instance known to the world, you can add it to the list over at Instances.social by filling out the admin form.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• Mastodon
• Fediverse
• ActivityPub
• Mastodon.social
• Code of conduct
• Mailgun
• List of Mastodon releases
• Mastodon blog
• Mastodon discussion forum
• Instances.social