Install php-apcu:

sudo apt-get install php5-apcu

Now download the latest package and install it:

wget https://releases.wikimedia.org/mediawiki/1.28/mediawiki-1.28.2.tar.gz
tar xvf mediawiki-1.28.2.tar.gz
mv mediawiki-1.28.2 wiki
chown -R www.www *

Now visit yoursite.com/wiki and complete installation there.
In your shell, create a mysql database, user and grant access:

mysql -u root -p
MariaDB [(none)]> create database if not exists mydbname;
use mydbname;
create user 'dbusr'@'localhost' identified by 'password';
grant all on mydbname.* to 'dbusr'@'localhost';
FLUSH PRIVILEGES;
quit;

Now use these auth details on the site.

After installation is done, to change password:
Find user by email id:

mysql -u root -p

show databases;
use oscewiki;
show tables;
SELECT user_name FROM wikiuser WHERE user_email = '[email protected]';
quit;

cd maintenance
sudo php changePassword.php --user=myusername --password=newpassword