The unattended-upgrades package used on Debian is based on the one from Ubuntu. It is generally pretty safe in my opinion but I only ever enable it for security upgrades.
Installation
apt-get install unattended-upgrades apticron
unattended-upgrades handles the actual updates, apticron is used for emailing you of available updates - it is not required but I like it.
Configuring unattended-upgrades
Open up /etc/apt/apt.conf.d/50unattended-upgrades and change it to the content below.
APT::Periodic::Enable "1"; APT::Periodic::Update-Package-Lists "1"; APT::Periodic::AutocleanInterval "7"; APT::Periodic::Unattended-Upgrade "1"; Unattended-Upgrade::Mail "**YOUR_EMAIL_HERE**"; // Automatically upgrade packages from these (origin, archive) pairs Unattended-Upgrade::Allowed-Origins { "${distro_id} stable"; "${distro_id} ${distro_codename}-security"; }; // Automatically reboot *WITHOUT CONFIRMATION* if a // the file /var/run/reboot-required is found after the upgrade Unattended-Upgrade::Automatic-Reboot "false";
So lets explain the above. As you can see we enable periodic updates, enable update package lists (triggers an apt-get update), enable autoclean …