Bookstack is a nice alternative to traditional wiki softwares. Here's a little guide to install it.

Step 1: Install dependencies

Run the following command to install all the latest php versions:

sudo apt install -y php php-fpm php-mysql php-curl php-mbstring php-ldap php-tidy php-xml php-zip php-gd composer
sudo apt install -y default-mysql-server default-mysql-client
sudo apt install -y sendmail

Step 2: Download the source code

Just run the following command to download the latest release of Bookstack.

git clone https://github.com/BookStackApp/BookStack.git --branch release --single-branch
cd BookStack

Step 3: Install from the source code

Just use composer and php to build and install from the source code.

composer install --no-dev

Step 4: Configure your database

Then we'll have to create our database for BookStack

mysql -u root
CREATE DATABASE bookstack_db;
CREATE USER 'bookstackuser'@'localhost' IDENTIFIED BY '<your password here>';
GRANT ALL PRIVILEGES ON bookstack_db.* TO 'bookstackuser'@'localhost';
FLUSH ALL PRIVILEGES;
EXIT;

Step 5: Configure the .env config file

First you need to rename the template .env.example into .env:

mv .env.example .env

Then you can change the database password in the file (and other variables according to your needs).

Step 6: Permissions

Now you need to make sure some directories are writable by the web server:

chown www-data:www-data -R /var/www/BookStack

Step 7: generate the application key and migrate the database

Very easy, simply run:

php artisan key:generate
php artisan migrate

Step 8: Make the URL rewrite rules in nginx

Now let's create a new configuration file in nginx:

nano /etc/nginx/sites-available/bookstack.conf

Then paste the following content (and replace books.example.com by your actual domain):

server {
    listen 80;
    listen [::]:80;

    server_name books.example.com;

    return 301 https://books.example.com$request_uri;
}

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;

    root /var/www/BookStack/public;

    include /etc/nginx/snippets/letsencrypt.conf;

    index index.php index.html index.htm;

    client_max_body_size 100M;

    location / {
        try_files $uri $uri/ /index.php?$query_string;
    }

    server_name books.example.com;

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/run/php/php7.4-fpm.sock;
        fastcgi_param   SCRIPT_FILENAME $document_root$fastcgi_script_name;
    }

    ssl_certificate /etc/letsencrypt/live/books.example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/books.example.com/privkey.pem;
    ssl_trusted_certificate /etc/letsencrypt/live/books.example.com/fullchain.pem;

    access_log /var/log/nginx/books.example.com.access.log;
    error_log /var/log/nginx/books.example.com.error.log;
}

Then, enable the configuration and restart nginx:

ln -s /etc/nginx/sites-available/bookstack.conf /etc/nginx/sites-enabled/
systemctl restart nginx

Step 9: Connect and change your password

Your instance of BookStack is now available on your subdomain, you can now connect using root account with the following credentials:

Of course don't forget to change them!

Conclusion

You should now have a full featured BookStack instance up and running.