This install guide is a how-to for installing DokuWiki Ubuntu server 20.04.

Packages required for DokuWiki to work:

sudo apt install php7.4 php7.4-common php7.4-cli php7.4-gd php7.4-mbstring php7.4-mysql php7.4-xml php7.4-ldap php7.4-fpm
sudo apt install nginx

First Check whether the mcrypt PHP module is present:

php -m | grep mcrypt

To install the mcrypt PHP module we first need to satisfy the following prerequisites:

sudo apt install php-dev libmcrypt-dev php-pear

Now we are ready to install mcrypt PHP module on our Ubuntu 20.04 system:

sudo pecl channel-update pecl.php.net
sudo pecl install mcrypt-1.0.4

Open the /etc/php/7.4/cli/php.ini file and insert:

extension=mcrypt.so

All done. When successful, checking for the presence of the mcrypt PHP module should produce the following output:

php -m | grep mcrypt
mcrypt

Download and extract DokuWiki stable to the proper directory.

wget -c https://download.dokuwiki.org/src/dokuwiki/dokuwiki-stable.tgz
mv dokuwiki-stable.tgz dokuwiki.tgz
sudo tar -xvf dokuwiki.tgz -C /var/www/

For SSL use the EFF's PPA for the Let's Encrypt certbot.

sudo add-apt-repository ppa:certbot/certbot
sudo apt update; sudo apt upgrade
sudo apt install python3-certbot-nginx
sudo certbot --nginx certonly

Cert and Key locations:

/etc/letsencrypt/live/wiki.domainname.tld/fullchain.pem
/etc/letsencrypt/live/wiki.domainname.tld/privkey.pem

source: https://certbot.eff.org/lets-encrypt/ubuntuxenial-nginx

sudo certbot renew

Need to make the configuration file for nginx to point to the correct files. Make sure to change the domain to the correct one, a generic placeholder wiki.domainname.tld is used for this example config.

sudo nano /etc/nginx/conf.d/dokuwiki.conf

Paste in the below configuration and save.

server {

listen 443 ssl;
 server_name wiki.domainname.tld;
 root /var/www/dokuwiki/;

access_log /var/log/nginx/dokuwiki.access.log;
 error_log /var/log/nginx/dokuwiki.error.log;

ssl on;
 ssl_certificate /etc/letsencrypt/live/wiki.domainname.tld/fullchain.pem;
 ssl_certificate_key /etc/letsencrypt/live/wiki.domainname.tld/privkey.pem;
 ssl_session_timeout 5m;
 ssl_ciphers 'AES256+EECDH:AES256+EDH:!aNULL';
 ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
 ssl_prefer_server_ciphers on;

add_header Content-Security-Policy "default-src 'self' 'unsafe-inline' 'unsafe-eval'; img-src 'self' data:;";
add_header X-XSS-Protection "1; mode=block";

index index.html index.php doku.php;

location / {
 try_files $uri $uri/ @dokuwiki;
 }

location @dokuwiki {
 rewrite ^/_media/(.*) /lib/exe/fetch.php?media=$1 last;
 rewrite ^/_detail/(.*) /lib/exe/detail.php?media=$1 last;
 rewrite ^/_export/([^/]+)/(.*) /doku.php?do=export_$1&id=$2 last;
 rewrite ^/(.*) /doku.php?id=$1 last;
 }

location ~ /(data|conf|bin|inc)/ {
 deny all;
 }

location ~* \.(css|js|gif|jpe?g|png)$ {
 expires 1M;
 add_header Pragma public;
 add_header Cache-Control "public, must-revalidate, proxy-revalidate";
 }

location ~ \.php$ {
 fastcgi_split_path_info ^(.+\.php)(/.+)$;
 fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
 fastcgi_index index.php;
 include fastcgi_params;
 fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
 fastcgi_intercept_errors off;
 fastcgi_buffer_size 16k;
 fastcgi_buffers 4 16k;
 }

location ~ /\.ht {
 deny all;
 }
}


server { 
 listen 80;
 server_name wiki.domainname.tld;
 add_header Strict-Transport-Security max-age=2592000;
 rewrite ^ https://wiki.domainname.tld$request_uri? permanent;
}

Here we are going to change the permissions on the web root files so that the web server can use and modify them.

sudo chown -R www-data:www-data /var/www/dokuwiki

Start nginx and php-fpm, and enable php-fpm to start at boot.

sudo systemctl start nginx php7.4-fpm
sudo systemctl enable php7.4-fpm

Navigate your browser to your https://wiki.domainname.tld/install.php

From there you can configure everything for the initial setup of DokuWiki.

Make userstyle.css in /conf

sudo vim /var/www/dokuwiki/conf/userstyle.css

Copy the following

.dokuwiki div.page {
	box-shadow: none;
}
.dokuwiki .pageId span {
	box-shadow: none;
}
pre {
	box-shadow: none;
}