The system can automatically install updates. If you want this, install unattended-upgrades package.vYou never miss a security update.
aptitude install unattended-upgrades
You must edit this file. Make a reconfiguration and select yes.
vi /etc/apt/apt.conf.d/50unattended-upgrades
....
Unattended-Upgrade::Allowed-Origins {
"${distro_id}:${distro_codename}-security";
"${distro_id}:${distro_codename}-updates";
"${distro_id}:${distro_codename}-proposed";
"${distro_id}:${distro_codename}-backports";
};
....
dpkg-reconfigure unattended-upgrades