1. Установить пакет

$ apt install adminer

2. Файл /etc/apache2/conf-available

/etc/apache2/conf-available/adminer.conf

Alias /adminer "/usr/share/adminer/adminer"
<Directory "/usr/share/webapps/adminer">
	AllowOverride All
	Options FollowSymlinks
	Order allow,deny
	Allow from all
	# php_admin_value open_basedir "/srv/:/tmp/:/usr/share/webapps/:/etc/webapps:/usr/share/pear/"
</Directory>

3. Создать алиас

$ cd /etc/apache2/conf-enabled
$ ln -s ../conf-available/adminer.conf

или

$ a2enconf adminer