How to Install Redmine 4.1 on Ubuntu 19.04/20.04

sudo apt install build-essential libmysqlclient-dev libmysqlclient-dev imagemagick libmagickwand-dev  libmagickcore-dev

sudo apt-get install -y dirmngr gnupg

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 561F9B9CAC40B2F7

sudo apt-get install -y apt-transport-https ca-certificates

sudo sh -c 'echo deb https://oss-binaries.phusionpassenger.com/apt/passenger focal main > /etc/apt/sources.list.d/passenger.list'

sudo apt-get update

sudo apt-get install apache2 apache2-dev libapache2-mod-passenger

sudo apt-get install mysql-server mysql-client 

sudo mysql_secure_installation

sudo mysql

CREATE DATABASE redmine CHARACTER SET utf8mb4;

CREATE USER 'redmineuser'@'%' IDENTIFIED WITH mysql_native_password BY 'password';

GRANT ALL ON redmine.* TO 'redmineuser'@'%';

FLUSH PRIVILEGES;

EXIT;

cd /opt

sudo git clone -b 4.1-stable --single-branch https://github.com/redmine/redmine.git

cd /opt/redmine

sudo cp /opt/redmine/config/database.yml.example /opt/redmine/config/database.yml

sudo nano /opt/redmine/config/database.yml

production:
adapter: mysql2
database: redmine
host: localhost
username: redmine
password: “{change-with-strong-password}”
encoding: utf8

sudo apt-add-repository ppa:brightbox/ruby-ng

sudo apt-get update

sudo apt-get install ruby2.6 ruby2.6-dev

sudo gem install bundler

cd /opt/redmine

sudo bundle config set --local without 'development test postgresql sqlite'

sudo bundle install

cd /opt/redmine/

sudo bundle exec rake generate_secret_token

sudo RAILS_ENV=production bundle exec rake db:migrate

sudo nano /etc/apache2/mods-available/passenger.conf

<IfModule mod_passenger.c>
 PassengerDefaultUser www-data
 PassengerRoot /usr/lib/ruby/vendor_ruby/phusion_passenger/locations.ini
 PassengerDefaultRuby /usr/bin/ruby
</IfModule>

sudo nano /etc/apache2/sites-available/redmine.conf

<VirtualHost *:80>
     ServerAdmin admin@example.com
     ServerName example.com
     ServerAlias www.example.com
     DocumentRoot /var/www/html/redmine
     PassengerAppRoot /opt/redmine

     <Directory /var/www/html/redmine>
         RailsBaseURI /redmine
     </Directory>

     ErrorLog ${APACHE_LOG_DIR}/error.log
     CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

sudo ln -s /opt/redmine/public /var/www/html/redmine

sudo chown -R www-data:www-data /opt/redmine

sudo chown -R www-data:www-data /var/www/html/redmine

 sudo a2ensite redmine

 sudo a2enmod passenger

 sudo a2enmod rewrite

 sudo systemctl restart apache2