+### apt::update
+
+Runs `apt-get update`, updating the list of available packages and their versions without installing or upgrading any packages.
+
+The update runs on the first Puppet run after you include the class, then whenever `notify => Exec['apt_update']` occurs---this should happen when config files get updated or other relevant changes occur. If you set the `always_apt_update` parameter, the update will run on every Puppet run.
+
+### Facts
+
+There are a few facts included in the apt module describing the state of the apt system:
+
+* `apt_updates` --- the number of updates available on the system
+* `apt_security_updates` --- the number of updates which are security updates
+* `apt_package_updates` --- the package names that are available for update. In Facter 2.0 and later, this will be a list type; in earlier versions, it is a comma-delimited string.
+* `apt_update_last_success` --- The date in epochtime that `apt-get update` last ran successfully. This is determined by reading the mtime of the file `/var/lib/apt/periodic/update-success-stamp`. That file is generated by the `/etc/apt/apt.conf.d/15update-stamp` file.