CiviCRM/upgrade

There is a long guide on how to upgrade CiviCRM for drupal

You should be familiar with all the steps described in the manual, and understand how the particular steps impact/affect your installation. The short version below is known to work with our setup, and with 'routine' upgrades.

Here is the short version:

1. backup your database(s) sudo ~/bin/backup.db.sh drupal sudo ~/bin/backup.db.sh civicrm
2. download the code wget https://download.civicrm.org/civicrm-4.6.5-drupal.tar.gz
3. put site in maintenance modedrush vset maintenance_mode 1 (Make sure you are also logged in as Admin)
4. move old code, and unpack new code mv civicrm /tmp/ && tar xvzf civicrm-4.6.5-drupal.tar.gz
5. run the upgrade script /civicrm/upgrade?reset=1
6. put site in operation modedrush vset maintenance_mode 0
7. toast

Note that in the event that you get errors, you may need to clear the cache: sudo -u www-data drush cache-clear civicrm

The even shorter version is to use drush civicrm-upgrade --tarfile=./sites/all/modules/contrib/civicrm-5.1.2-drupal.tar.gz --backup-dir=/tmp/ does all the above for you.