Before running an update, please ensure that you have a full backup of your site. TKLBAM is recommended for this purpose.

To update use the desired commands below and follow the prompts. Please ensure that you read any warning carefully before proceeding.

For those who wish to only apply security updates using Drush (with full Drush commands, including enabling maintenance mode before, and disabling after):

drush pm-updatestatus
drush vset -y maintenance_mode 1
drush pm-update --security-only --simulate
drush pm-update --security-only
drush vset -y maintenance_mode 0

To update all modules using Drush, i.e. living dangerously! (using Drush alias):

drush vset -y maintenance_mode 1
drush up
drush vset -y maintenance_mode 0

To update Drush itself (to latest v8.x):

cd /usr/local/src/drush
git remote set-branches origin '8.x'
git fetch -v
# the composer.lock file was uncommited so git complains
git add .
git commit -m "commit composer.lock"
# continue on...
git checkout 8.x
composer install

Note: These docs update 2018-04-03 as drush 7.x is no longer supported. To see which drush version supports which versions of Drupal, please see the Drush install Drupal compatibility matrix