WordPress has their own guide to upgrade wordpress, but in this post I will show you how I upgrade my all wordpress sites.
I using Ubuntu 14.04 server and I update wordpress from command line.
Before upgrade we backup our database and wordpress directory.
$ mkdir -p ~/backup $ mysqldump -u user -p <database name> | gzip -9 > ~/backup/$(date +"%Y%m%d")_wordpress.sql.gz $ tar -zcvf ~/backup/$(date +"%Y%m%d")_wordpress-dir.tar.gz /home/niko/public_html/
$ cd /tmp/ $ wget https://wordpress.org/latest.zip $ unzip latest.zip
Overwrite all new files
Remember change current directory to where wordpress located in your server.
$ cd ~/public_html/ $ cp -avr /tmp/wordpress/* . $ rm -rf /tmp/wordpress /tmp/latest.zip
Open http://your_domain.com/wp-admin/upgrade.php in a browser and run that script. It makes all needed database conversions. If something fails, you still have your backups in ~/backup/ directory.