Convert WordPress to Multisite

Connect to the VM as root and save a copy of the site files and database. This assumes the database is named wordpress; use your own name if it differs.

ssh root@YOUR_SERVER_IP

mkdir -p /root/wp-backup
mariadb-dump wordpress > /root/wp-backup/wordpress-$(date +%F).sql
tar -czf /root/wp-backup/wp-files-$(date +%F).tar.gz -C /var/www/html .
ls -lh /root/wp-backup

Download these files to another machine so a VM failure cannot take your only copy with it.

In the WordPress dashboard, open Plugins, select every plugin, and choose Deactivate. This avoids conflicts during conversion. You will reactivate them afterward.

Also check that your permalinks work and that Settings → General shows the correct site address.

Open wp-config.php and add the line below on its own line above the comment that says That’s all, stop editing!

nano /var/www/html/wp-config.php

define( 'WP_ALLOW_MULTISITE', true );

In nano, press Ctrl+O then Enter to save, and Ctrl+X to exit.

Reload the dashboard and open Tools → Network Setup. Choose Sub-domains or Sub-directories, set the network title and administrator email, and select Install.

WordPress then shows two code blocks made for your site, one for wp-config.php and one for .htaccess. Keep that page open and copy from it in the next steps.

Use your own screen’s code: The examples below show the shape of what WordPress generates, but the Network Setup page contains your real domain and your chosen type. Prefer its values if they differ.

Open wp-config.php again and paste WordPress’s first code block below the WP_ALLOW_MULTISITE line, still above the stop editing comment. Example for a subdirectory network, where example.com is your domain:

define( 'MULTISITE', true );
define( 'SUBDOMAIN_INSTALL', false );
define( 'DOMAIN_CURRENT_SITE', 'example.com' );
define( 'PATH_CURRENT_SITE', '/' );
define( 'SITE_ID_CURRENT_SITE', 1 );
define( 'BLOG_ID_CURRENT_SITE', 1 );

For a subdomain network, SUBDOMAIN_INSTALL is true instead.

Open .htaccess and replace the existing block between # BEGIN WordPress and # END WordPress with WordPress’s second code block. Copy the version that matches your network type.

nano /var/www/html/.htaccess

Sub-directory network

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

Sub-domain network

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]

Return to the WordPress login page and sign in again. You should now see My Sites → Network Admin in the admin bar. Open this address to reach the network dashboard:

Replace example.com with your domain, and use http if you have not enabled HTTPS.

apache2ctl configtest && systemctl reload apache2

In Network Admin → Sites → Add New, create your first extra site by entering its address, title, and administrator email. Then go to Network Admin → Plugins and use Network Activate for plugins every site should have. Plugins that should run on only some sites can be activated from each site’s own dashboard.

Some plugins and themes are not multisite compatible. Test each one after activating it, and enable themes for the network under Network Admin → Themes.

Add a wildcard DNS record, *.example.com, pointing to the VM’s IP address, and make sure Apache’s default site answers all hostnames. A standard single-site certificate does not cover new subdomains. Wildcard certificates from Let’s Encrypt require DNS validation, so follow Certbot’s instructions for your DNS provider.

If conversion fails, restore the snapshot or the backup from Step 01. To restore the backup, replace the date in each file name, then run the commands. This overwrites the current site and database.

mariadb wordpress < /root/wp-backup/wordpress-YYYY-MM-DD.sql
tar -xzf /root/wp-backup/wp-files-YYYY-MM-DD.tar.gz -C /var/www/html
chown -R www-data:www-data /var/www/html
systemctl reload apache2

Before running: Restoring replaces everything changed since the backup, including posts and uploads. Check the file names first with ls /root/wp-backup.