Keeping your computer up to date is the single most important task for protecting your computer. Ubuntu can alert you to pending updates, and also be configured to apply updates automatically. Security updates for Ubuntu are announced via Ubuntu Security Notices (USNs).
By default, users are notified daily for security updates and weekly for non-security updates. How Ubuntu alerts you as well as configuring your system to install updates automatically can be setup within Update Manager. You can access Update Manager anytime by pressing 'Alt+F2', entering update-manager and pressing Enter. Its settings can be adjusted by pressing the 'Settings' button.
Once Update Manager is open, you can review and select pending updates as well as check for new updates. Simply press the 'Install Updates' button to upgrade the selected packages to the updated version.
If the update-notifier-common package is installed, Ubuntu will alert you about pending updates via the message of the day (motd) upon console or remote login.
After logging in, you can check for and apply new updates with:
$ sudo apt-get update $ sudo apt-get dist-upgrade
When performing an update, first review what apt is going to do, then confirm that you want to apply the updates (this is particularly true when running the development release).
If you would prefer to have updates applied automatically, make sure the unattended-upgrades package is installed, then run sudo dpkg-reconfigure unattended-upgrades. Please note that updates may restart services on your server, so this may not be appropriate for all environments.